Where can I learn Energy conservation for Cambridge 9702?

This free lesson on MarkScheme covers syllabus point 5.1 (Energy conservation) for Cambridge A-Level Physics. It includes visual revision, key points, and links to real past-paper questions with mark-scheme marking at markscheme.app/courses/9702/5-1-energy-conservation.

Is Energy conservation (5.1) on 9702 free to study?

Yes. The Physics 9702 course on MarkScheme is 100% free — including premium visual lessons, exam tips, and past-paper marking. No paywall for Energy conservation.

How do I revise Energy conservation for 9702 exams?

Start with the visual steps on this page, note the key exam points, then attempt a 9702 past-paper question on Energy conservation using MarkScheme's /mark tool. Mark strictly against the official scheme and re-read any marks you lost.

MarkScheme 9702

Opening…

5.1Physics25 min readPREMIUM

Energy conservation

Ever wondered why a bouncing ball eventually stops? Or how a rollercoaster gains incredible speed? It all comes down to energy conservation – a fundamental principle in Physics that explains how energy transforms from one form to another without ever being lost or created. This pilot aligns with Senpai Corner AS notes (2025–2027) for topic 5.1.

BY THE END, YOU CAN…

exam checklist — tick these off

1Apply the principle of energy conservation to solve problems.
2Calculate kinetic and gravitational potential energy changes using relevant formulas.
3Understand and calculate work done (including when force is at an angle to displacement), power, and efficiency in various physical systems.

STUDY MODE

READING

TYPEFACE

Literata — a reading serif made for e-books; set like a textbook, sits well beside maths.

SIZE

AIRY SPACING

Wider letter and line spacing. The one change with solid evidence for readers who lose their place — worth a try whoever you are.

Pick whatever reads fastest for you — it differs from person to person, by up to a third.

EXPLAIN SIMPLER

The same notes in plain English — no jargon. Key points and exam tips stay.

DIAGRAM NOTES

A small sketch beside each block of notes.

In simple terms

A friendly intro before the formal notes — no formulas yet.

Energy conservation

Cambridge 9702 Paper 2 — Energy conservation (5.1). Senpai Corner diagram-backed pilot with premium structure and live visuals.

1
5.1 Energy conservation.
2
In physics, work (W) is the energy transferred to or from an object through the application of force (F) along a displacement (d) 𝑊 = 𝐹 × 𝑑.
3
The SI units for work is in Joules.
4
The principle of conservation of energy states that energy is neither created nor destroyed. But may transform from one type to another .

What this topic covers

The official Cambridge syllabus points this lesson works through.

5.1.1
Understand the concept of work, and recall and use work done = force × displacement in the direction of the force
5.1.2
Recall and apply the principle of conservation of energy
5.1.3
Recall and understand that the efficiency of a system is the ratio of useful energy output from the system to the total energy input
5.1.4
Use the concept of efficiency to solve problems
5.1.5
Define power as work done per unit time
5.1.6
Solve problems using $P = W/t$
5.1.7
Derive $P = Fv$ and use it to solve problems

Explore the concept

Use the live diagram, PhET or GeoGebra sim, and synced steps — play it, drag controls, or tap a step.

Figure PhET simulation1 / 4

Loading simulation…

Fetching from PhET…

Energy Skate Park

Total energy is constant; friction converts mechanical energy to thermal, never destroys it.

If the embed does not load, use Open on PhET.

Simulation by PhET Interactive Simulations, University of Colorado Boulder · Licensed to MarkScheme (public licence CC BY-NC 4.0 since 2026-03-30)

Step-synced diagram — highlights what to look for in the simulation above.

Step 1

5.1 Energy conservation.

23 more simulations for this topic — run them in the Simulations section below

Simulations

Every simulation here runs the real model — try the steps on a card, then check what you see against the notes.

23 simulations · 5 to start with

Start herein this order — each one shows a different piece of the topic

The Physics ClassroomStart here · 19702 5.1 · 9702 5.2 · IB A.3
It's All Uphill
Drive a car up a gently-sloped hill and a steep hill to the same summit and compare the work and energy
Why this one: Gentle or steep hill to the same summit: work against gravity depends only on height gained.
Try this
1. Drive up the gentle hill and read the work done.
2. Drive up the steep hill to the same summit.
3. Compare the two values.
Look for Work done against gravity depends only on the height gained, not on the slope.
Open on The Physics Classroom
Physics Interactives by The Physics Classroom · Licensed to MarkScheme (site terms otherwise permit linking only)
3JCN PhysicsStart here · 29702 5.1 · 9702 5.2 · 9702 3.1
Work-Energy & Friction Floor
Push a block across a rough floor; compare work done by force and by friction with the KE change
Why this one: Change in KE equals work done by the push minus work done against friction.
Try this
1. Push the block across the rough floor and read the work done by the force.
2. Read the work done by friction and the KE change.
3. Compare the KE change with the net work.
Look for The change in KE equals the work done by the applied force minus the work done against friction.
Open on 3JCN Physics
3JCN Physics Simulation by Thomas Nguyen · CC BY 4.0
The Physics ClassroomStart here · 39702 5.1 · 9702 5.2 · IB A.3
Kinetic Energy
Relate the work done on an object to the kinetic energy it acquires, and see what friction changes
Why this one: Net work done on the object equals the kinetic energy it gains; add friction and see the shortfall.
Try this
1. Apply a force and read the kinetic energy gained.
2. Add friction and compare the kinetic energy.
Look for Net work done equals the change in kinetic energy.
Open on The Physics Classroom
Physics Interactives by The Physics Classroom · Licensed to MarkScheme (site terms otherwise permit linking only)
3JCN PhysicsStart here · 49702 5.1 · 9702 5.2 · IB A.3
CoE on an Inclined Ramp
Slide a block down a ramp with chosen height and friction; track energy transfers
Why this one: With friction the missing KE at the bottom equals the work done against the resistive force.
Try this
1. Set a height with no friction and slide the block; track the energy transfers.
2. Add friction and compare the KE at the bottom.
Look for Without friction PE converts fully to KE; with friction the missing KE equals the work done against friction.
Open on 3JCN Physics
3JCN Physics Simulation by Thomas Nguyen · CC BY 4.0
The Physics ClassroomStart here · 59702 5.1 · IB A.3
Chart That Motion
Build work-energy bar charts that show what happens to the total energy of an object and how its form changes
Why this one: Build energy bar charts: the total height only changes when external work is done.
Try this
1. Fill the bars for a falling object.
2. Fill the bars for a case with friction.
3. Check the totals.
Look for The total height of the bars is unchanged unless external work is done.
Open on The Physics Classroom
Physics Interactives by The Physics Classroom · Licensed to MarkScheme (site terms otherwise permit linking only)

More simulations18 more on this topic — core ones first

PhETCoreJava · best on a laptop9702 5.1 · 3.1 · 4.2 · IB A.3 · A.2
The Ramp
Push objects up a ramp; vary the angle, friction and mass and read the work done, energy bar charts and force graphs.
Try this
1. Push a crate to the top at 15° with friction off — read the work done and the GPE gained.
2. Turn friction on and repeat — the extra work shows up as thermal energy.
3. Steepen the ramp — more force per metre, but the same GPE at the top.
Look for Work done = gain in GPE + energy lost to friction; the ramp trades force for distance.
Open on PhET
Simulation by PhET Interactive Simulations, University of Colorado Boulder · Licensed to MarkScheme (public licence CC BY-NC 4.0 since 2026-03-30)
oPhysicsCore9702 3.3 · 9702 5.1 · IB A.2
Momentum & Energy: Elastic and Inelastic Collisions
1D collision of two masses: set masses, velocities and elasticity; compare momentum and KE before/after
Try this
1. Set equal masses, one at rest, fully elastic; compare the velocities after.
2. Make the collision fully inelastic with the same setup.
3. Give one mass twice the other and run both elasticities.
Look for Momentum is the same before and after in every case; kinetic energy is conserved only when the collision is elastic.
Open on oPhysics
Simulation by Tom Walsh, oPhysics.com — made with GeoGebra · Licensed to MarkScheme (site: free for non-profit educational use; applets made with GeoGebra)
oPhysicsCore9702 3.3 · 9702 5.1 · IB A.2
The Ballistic Pendulum
Ballistic pendulum: set bullet/block masses and bullet speed; see inelastic collision then rise height
Try this
1. Set a bullet speed and read the rise height.
2. Double the bullet speed and compare the rise height.
3. Increase the block mass with the same bullet speed.
Look for Momentum is conserved in the collision and energy afterwards, so the rise height grows with the square of the bullet speed.
Open on oPhysics
Simulation by Tom Walsh, oPhysics.com — made with GeoGebra · Licensed to MarkScheme (site: free for non-profit educational use; applets made with GeoGebra)
oPhysicsCore9702 3.3 · 9702 5.1 · IB A.2
Ballistic Pendulum "Quiz"
Ballistic pendulum quiz: given masses and rise height, compute the bullet speed and check it
Try this
1. Read the masses and rise height and compute the speed just after impact.
2. Use momentum conservation to find the bullet speed and check it.
3. Reset for a new set of values and repeat.
Look for The speed just after impact comes from the rise height, and the bullet speed from momentum conservation.
Open on oPhysics
Simulation by Tom Walsh, oPhysics.com — made with GeoGebra · Licensed to MarkScheme (site: free for non-profit educational use; applets made with GeoGebra)
oPhysicsCore9702 5.1 · 9702 5.2 · 9702 17.2
Conservation of Mechanical Energy: Mass on a Vertical Spring
Mass oscillating on a vertical spring with live KE / GPE / EPE bar graphs; adjust mass and spring constant
Try this
1. Watch the three bars through one full oscillation.
2. Increase the mass and compare the bar heights.
3. Increase the spring constant and compare the period.
Look for KE, GPE and EPE trade against each other while their total stays constant.
Open on oPhysics
Simulation by Tom Walsh, oPhysics.com — made with GeoGebra · Licensed to MarkScheme (site: free for non-profit educational use; applets made with GeoGebra)
The Physics ClassroomCore9702 3.1 · 9702 4.2 · 9702 5.1
Inclined Plane Simulation
Set the angle, mass, initial velocity and coefficients of static and kinetic friction; observe the forces, motion and energy changes
Try this
1. Set both friction coefficients to zero and vary the angle.
2. Add kinetic friction and compare the acceleration.
3. Increase the mass and compare the acceleration.
Look for Acceleration down a slope is g(sin θ − μ cos θ), independent of mass.
Open on The Physics Classroom
Physics Interactives by The Physics Classroom · Licensed to MarkScheme (site terms otherwise permit linking only)

Key formulas

Tap any symbol to reveal exactly what it means and its units.

KEY RELATION

$KE = \frac{1}{2}mv^2$

Tap a symbol — great for exam definitions

KEY RELATION

$GPE = mgh \text{ or } \Delta GPE = mg\Delta h$

Tap a symbol — great for exam definitions

KEY RELATION

= Fd

Tap a symbol — great for exam definitions

KEY RELATION

$W = Fd \cos \theta$

Tap a symbol — great for exam definitions

KEY RELATION

$P = \frac{\Delta E}{\Delta t} \text{ and } P = Fv$

Tap a symbol — great for exam definitions

KEY RELATION

$Efficiency = \frac{\text{Useful Energy Output}}{\text{Total Energy Input}} = \frac{\text{Useful Power Output}}{\text{Total Power Input}}$

Tap a symbol — great for exam definitions

Full topic notes

Formal explanation with the rigour you need for the exam.

The Unbreakable Rule: Conservation of Energy

At its core, the Principle of Conservation of Energy states that energy can neither be created nor destroyed. Instead, it continuously changes from one form to another. In a closed system, where no energy can enter or leave, the total amount of energy always stays constant.

5.1 Energy conservation.
In physics, work (W) is the energy transferred to or from an object through the application of force (F) along a displacement (d) 𝑊 = 𝐹 × 𝑑.
The SI units for work is in Joules.
The principle of conservation of energy states that energy is neither created nor destroyed. But may transform from one type to another .
E.g. work can be transformed to heat (friction!), electric to light.
Not all energy transferred is useful. E.g. when transferring electric to light, some energy is wasted in the form of heat!.

Not clear?

Energy's Many Forms: Kinetic and Gravitational Potential

Two crucial forms of energy we frequently encounter are Kinetic Energy (KE) and Gravitational Potential Energy (GPE). KE is the energy an object possesses due to its motion, while GPE is the energy stored due to its position in a gravitational field.

$KE = \frac{1}{2}mv^2$

Kinetic energy depends on an object's mass ( $m$ ) and the square of its velocity ( $v$ ). The faster or more massive an object, the more kinetic energy it has.

$GPE = mgh \text{ or } \Delta GPE = mg\Delta h$

Gravitational potential energy depends on mass ( $m$ ), gravitational acceleration ( $g$ ), and vertical height ( $h$ ). You can choose any convenient reference point for 'h', as only the change in height matters for $\Delta GPE$ .

Kinetic energy is related to an object's movement.
GPE is energy stored by an object's height in a gravitational field.
KE is proportional to mass and the square of velocity.
GPE depends on mass, gravity, and vertical height change.
The GPE reference height can be set arbitrarily.

Not clear?

Work, Power, and Efficiency: Energy in Action

When energy is transferred, we call it work done. Work is done when a force causes an object to move a certain distance. Think of pushing a box across a floor – you're doing work on it. If the force and displacement are in the same direction, the calculation is simple:

$W = Fd$

What if the force is not in the same direction as the displacement? For example, pulling a suitcase with a handle at an angle. In this case, only the component of the force that acts in the direction of motion does work. We use the formula:

$W = Fd \cos \theta$

Here, $\theta$ is the angle between the force vector and the displacement vector. If the force is perpendicular to the displacement ( $\theta = 90°$ ), then $\cos(90°) = 0$ , and no work is done. This is why the gravitational force does no work on an object moving horizontally.

Power is how quickly this energy transfer or work happens. A powerful engine can do a lot of work in a short amount of time, indicating a high rate of energy transfer.

$P = \frac{\Delta E}{\Delta t} \text{ and } P = Fv$

The formula $P = Fv$ is particularly useful for objects moving at a constant velocity $v$ against a constant force $F$ . It's derived from $P = W/t = (Fd)/t$ and knowing that $v = d/t$ for constant velocity.

Finally, efficiency tells us how effectively a system converts input energy into useful output energy. No real system is 100% efficient because some energy is always 'lost' to unwanted forms, typically heat or sound. For example, an electric motor lifting a mass gains useful GPE, but some input electrical energy is wasted as heat in the motor's coils and sound from its operation.

$Efficiency = \frac{\text{Useful Energy Output}}{\text{Total Energy Input}} = \frac{\text{Useful Power Output}}{\text{Total Power Input}}$

Work done is energy transferred by a force causing displacement.
Use $W = Fd \cos \theta$ when force and displacement are at an angle $\theta$ .
Power measures the rate of energy transfer or work done.
For constant velocity, power can be calculated as $P = Fv$ .
Efficiency compares useful output energy/power to total input energy/power.
Real systems always have efficiency less than 100% due to energy losses.

Not clear?

Worked examples

See the formulas applied — reveal one step at a time, like the exam.

reveal slowly — mark each step

EXAMPLE 1

A 2.0 kg ball is dropped from a height of 5.0 m. (a) Calculate its gravitational potential energy at the start. (b) Assuming no air resistance, calculate its speed just before hitting the ground. (c) If, due to air resistance, its actual speed just before hitting the ground is 8.5 m/s, calculate the work done against air resistance. (Take $g = 9.81 \text{ m/s}^2$ ).

1
(a) Initial GPE: $GPE = mgh = 2.0 \text{ kg} \times 9.81 \text{ m/s}^2 \times 5.0 \text{ m} = 98.1 \text{ J}$.

EXAMPLE 2

A car of mass 1200 kg travels at a constant speed of 18 m/s up a road inclined at 6.0° to the horizontal. The car's engine works at a constant rate of 45 kW. (a) Calculate the work done against the gravitational force in 10 seconds. (b) Calculate the total work done by the engine in 10 seconds. (c) Determine the magnitude of the total resistive force acting on the car. (Take $g = 9.81 \text{ m/s}^2$ ).

1
(a) First, find the vertical height gained in 10 seconds.

How it all connects

The big idea sits in the middle — tap a linked idea to explore the link.

MAIN IDEAEnergy conservation

Tap a linked idea to see how it connects back to the main topic — that connection is what examiners reward.

Glossary

Key terms for this topic — skim now; the Check step will test them.

Principle of Conservation of Energy: At its core, the Principle of Conservation of Energy states that energy can neither be created nor destroyed.
Power: Power is how quickly this energy transfer or work happens. A powerful engine can do a lot of work in a short amount of time, indicating a high rate of energy transfer.
Closed system: Energy cannot be created or destroyed, only transformed, so the total energy remains constant.

10Apply

Quick check

Write your answer first, then compare it with the model one — the gap is what you would have lost.

0 of 6 answered

11Understand

Teach it back

If you can explain it simply, you own it — gaps here are marks you’d lose.

Teach it back

Explain this topic as if teaching a friend. We name the gaps an examiner would still dock.

Your explanation — no notes

12Remember

Revision flashcards

Guess first, then flip — retrieval beats re-reading.

Your guess — write it before you look

1 / 15 · ← → space

Key takeaways

Review these before you close the topic — retrieval beats re-reading.

close the tab only after these stick

5.1 Energy conservation.
In physics, work (W) is the energy transferred to or from an object through the application of force (F) along a displacement (d) 𝑊 = 𝐹 × 𝑑.
The SI units for work is in Joules.
The principle of conservation of energy states that energy is neither created nor destroyed. But may transform from one type to another .
E.g. work can be transformed to heat (friction!), electric to light.
Not all energy transferred is useful. E.g. when transferring electric to light, some energy is wasted in the form of heat!.

Practice — then mark it

The whole point: a real Cambridge question, marked mark-by-mark.

Question 1 of 29702/22 · Q3(b)

PhysicsMay/June 2024

(b)

The potential difference between the ground and the atmosphere is 3.0 × 10^7 V.

Calculate the average power, in GW, transferred during the lightning strike.

power = ................................................................ GW

Do it on paper → mark itMARKED MARK-BY-MARK · B1 / M1 / A1 · OFFICIAL SCHEME

9702/22/M/J/24

Question 2 of 29702/23 · Q3(d)

PhysicsMay/June 2024

(d)

Determine an estimate of the work done on the sample as it is extended from zero extension to its breaking point. Explain your reasoning.

Do it on paper → mark itMARKED MARK-BY-MARK · B1 / M1 / A1 · OFFICIAL SCHEME

9702/23/M/J/24

Extra simulations & links

PhET, GeoGebra and other curated tools — open in a new tab.

Frequently asked

Why is it impossible for a machine to be 100% efficient?

When should I use

W = Fd

versus

W = Fd \cos \theta

for work done?

Can gravitational potential energy ever be negative?

Checkpoint

One marked question is worth ten re-reads — close the loop before you move on.

Checkpoint

Reading it isn’t knowing it — prove it.

Before you move on: do 9702/22 · Q3(b) on paper, snap a photo, and get examiner-style feedback on exactly where you win and lose marks.

Attempt & get marked →Takes about a minute · you’ll land back on this lesson

← PREVIOUS4.3 Density and pressure NEXT →5.2 Gravitational potential energy and kinetic energy

Discuss Energy conservation

Ask, share and discuss with other Physics students

19702 Physics: June 2026 thresholds are out — post your components1 #1How did everyone find the June 2026 Physics A-Level papers?3 #14Why is centripetal force not a real force?2 #2Interesting Diagram0 #

Create a post Visit s/9702

Revise Energy conservation for Cambridge 9702 (5.1)

Looking for free Physics 9702 notes on Energy conservation? This A-Level lesson covers official syllabus point 5.1 on Paper 1: Multiple Choice / Paper 2: AS Level Structured Questions. Use the visual steps, key terms, and quick checks below — then practise a real 9702 past-paper question with mark-scheme marking. Built for students searching "Energy conservation 9702 revision", "9702 5.1 notes", or a free alternative to paid note sites.

Full Physics 9702 course Mark a past paper →9702 subject hub

5.1Physics25 min readPREMIUM

Energy conservation

BY THE END, YOU CAN…

exam checklist — tick these off

1Apply the principle of energy conservation to solve problems.
2Calculate kinetic and gravitational potential energy changes using relevant formulas.
3Understand and calculate work done (including when force is at an angle to displacement), power, and efficiency in various physical systems.

STUDY MODE

READING

TYPEFACE

Literata — a reading serif made for e-books; set like a textbook, sits well beside maths.

SIZE

AIRY SPACING

Wider letter and line spacing. The one change with solid evidence for readers who lose their place — worth a try whoever you are.

Pick whatever reads fastest for you — it differs from person to person, by up to a third.

EXPLAIN SIMPLER

The same notes in plain English — no jargon. Key points and exam tips stay.

DIAGRAM NOTES

A small sketch beside each block of notes.

In simple terms

A friendly intro before the formal notes — no formulas yet.

Energy conservation

Cambridge 9702 Paper 2 — Energy conservation (5.1). Senpai Corner diagram-backed pilot with premium structure and live visuals.

1
5.1 Energy conservation.
2
In physics, work (W) is the energy transferred to or from an object through the application of force (F) along a displacement (d) 𝑊 = 𝐹 × 𝑑.
3
The SI units for work is in Joules.
4
The principle of conservation of energy states that energy is neither created nor destroyed. But may transform from one type to another .

What this topic covers

The official Cambridge syllabus points this lesson works through.

5.1.1
Understand the concept of work, and recall and use work done = force × displacement in the direction of the force
5.1.2
Recall and apply the principle of conservation of energy
5.1.3
Recall and understand that the efficiency of a system is the ratio of useful energy output from the system to the total energy input
5.1.4
Use the concept of efficiency to solve problems
5.1.5
Define power as work done per unit time
5.1.6
Solve problems using $P = W/t$
5.1.7
Derive $P = Fv$ and use it to solve problems

Explore the concept

Use the live diagram, PhET or GeoGebra sim, and synced steps — play it, drag controls, or tap a step.

Figure PhET simulation1 / 4

Loading simulation…

Fetching from PhET…

Energy Skate Park

Total energy is constant; friction converts mechanical energy to thermal, never destroys it.

If the embed does not load, use Open on PhET.

Simulation by PhET Interactive Simulations, University of Colorado Boulder · Licensed to MarkScheme (public licence CC BY-NC 4.0 since 2026-03-30)

Step-synced diagram — highlights what to look for in the simulation above.

Step 1

5.1 Energy conservation.

23 more simulations for this topic — run them in the Simulations section below

Simulations

Every simulation here runs the real model — try the steps on a card, then check what you see against the notes.

23 simulations · 5 to start with

Start herein this order — each one shows a different piece of the topic

The Physics ClassroomStart here · 19702 5.1 · 9702 5.2 · IB A.3
It's All Uphill
Drive a car up a gently-sloped hill and a steep hill to the same summit and compare the work and energy
Why this one: Gentle or steep hill to the same summit: work against gravity depends only on height gained.
Try this
1. Drive up the gentle hill and read the work done.
2. Drive up the steep hill to the same summit.
3. Compare the two values.
Look for Work done against gravity depends only on the height gained, not on the slope.
Open on The Physics Classroom
Physics Interactives by The Physics Classroom · Licensed to MarkScheme (site terms otherwise permit linking only)
3JCN PhysicsStart here · 29702 5.1 · 9702 5.2 · 9702 3.1
Work-Energy & Friction Floor
Push a block across a rough floor; compare work done by force and by friction with the KE change
Why this one: Change in KE equals work done by the push minus work done against friction.
Try this
1. Push the block across the rough floor and read the work done by the force.
2. Read the work done by friction and the KE change.
3. Compare the KE change with the net work.
Look for The change in KE equals the work done by the applied force minus the work done against friction.
Open on 3JCN Physics
3JCN Physics Simulation by Thomas Nguyen · CC BY 4.0
The Physics ClassroomStart here · 39702 5.1 · 9702 5.2 · IB A.3
Kinetic Energy
Relate the work done on an object to the kinetic energy it acquires, and see what friction changes
Why this one: Net work done on the object equals the kinetic energy it gains; add friction and see the shortfall.
Try this
1. Apply a force and read the kinetic energy gained.
2. Add friction and compare the kinetic energy.
Look for Net work done equals the change in kinetic energy.
Open on The Physics Classroom
Physics Interactives by The Physics Classroom · Licensed to MarkScheme (site terms otherwise permit linking only)
3JCN PhysicsStart here · 49702 5.1 · 9702 5.2 · IB A.3
CoE on an Inclined Ramp
Slide a block down a ramp with chosen height and friction; track energy transfers
Why this one: With friction the missing KE at the bottom equals the work done against the resistive force.
Try this
1. Set a height with no friction and slide the block; track the energy transfers.
2. Add friction and compare the KE at the bottom.
Look for Without friction PE converts fully to KE; with friction the missing KE equals the work done against friction.
Open on 3JCN Physics
3JCN Physics Simulation by Thomas Nguyen · CC BY 4.0
The Physics ClassroomStart here · 59702 5.1 · IB A.3
Chart That Motion
Build work-energy bar charts that show what happens to the total energy of an object and how its form changes
Why this one: Build energy bar charts: the total height only changes when external work is done.
Try this
1. Fill the bars for a falling object.
2. Fill the bars for a case with friction.
3. Check the totals.
Look for The total height of the bars is unchanged unless external work is done.
Open on The Physics Classroom
Physics Interactives by The Physics Classroom · Licensed to MarkScheme (site terms otherwise permit linking only)

More simulations18 more on this topic — core ones first

PhETCoreJava · best on a laptop9702 5.1 · 3.1 · 4.2 · IB A.3 · A.2
The Ramp
Push objects up a ramp; vary the angle, friction and mass and read the work done, energy bar charts and force graphs.
Try this
1. Push a crate to the top at 15° with friction off — read the work done and the GPE gained.
2. Turn friction on and repeat — the extra work shows up as thermal energy.
3. Steepen the ramp — more force per metre, but the same GPE at the top.
Look for Work done = gain in GPE + energy lost to friction; the ramp trades force for distance.
Open on PhET
Simulation by PhET Interactive Simulations, University of Colorado Boulder · Licensed to MarkScheme (public licence CC BY-NC 4.0 since 2026-03-30)
oPhysicsCore9702 3.3 · 9702 5.1 · IB A.2
Momentum & Energy: Elastic and Inelastic Collisions
1D collision of two masses: set masses, velocities and elasticity; compare momentum and KE before/after
Try this
1. Set equal masses, one at rest, fully elastic; compare the velocities after.
2. Make the collision fully inelastic with the same setup.
3. Give one mass twice the other and run both elasticities.
Look for Momentum is the same before and after in every case; kinetic energy is conserved only when the collision is elastic.
Open on oPhysics
Simulation by Tom Walsh, oPhysics.com — made with GeoGebra · Licensed to MarkScheme (site: free for non-profit educational use; applets made with GeoGebra)
oPhysicsCore9702 3.3 · 9702 5.1 · IB A.2
The Ballistic Pendulum
Ballistic pendulum: set bullet/block masses and bullet speed; see inelastic collision then rise height
Try this
1. Set a bullet speed and read the rise height.
2. Double the bullet speed and compare the rise height.
3. Increase the block mass with the same bullet speed.
Look for Momentum is conserved in the collision and energy afterwards, so the rise height grows with the square of the bullet speed.
Open on oPhysics
Simulation by Tom Walsh, oPhysics.com — made with GeoGebra · Licensed to MarkScheme (site: free for non-profit educational use; applets made with GeoGebra)
oPhysicsCore9702 3.3 · 9702 5.1 · IB A.2
Ballistic Pendulum "Quiz"
Ballistic pendulum quiz: given masses and rise height, compute the bullet speed and check it
Try this
1. Read the masses and rise height and compute the speed just after impact.
2. Use momentum conservation to find the bullet speed and check it.
3. Reset for a new set of values and repeat.
Look for The speed just after impact comes from the rise height, and the bullet speed from momentum conservation.
Open on oPhysics
Simulation by Tom Walsh, oPhysics.com — made with GeoGebra · Licensed to MarkScheme (site: free for non-profit educational use; applets made with GeoGebra)
oPhysicsCore9702 5.1 · 9702 5.2 · 9702 17.2
Conservation of Mechanical Energy: Mass on a Vertical Spring
Mass oscillating on a vertical spring with live KE / GPE / EPE bar graphs; adjust mass and spring constant
Try this
1. Watch the three bars through one full oscillation.
2. Increase the mass and compare the bar heights.
3. Increase the spring constant and compare the period.
Look for KE, GPE and EPE trade against each other while their total stays constant.
Open on oPhysics
Simulation by Tom Walsh, oPhysics.com — made with GeoGebra · Licensed to MarkScheme (site: free for non-profit educational use; applets made with GeoGebra)
The Physics ClassroomCore9702 3.1 · 9702 4.2 · 9702 5.1
Inclined Plane Simulation
Set the angle, mass, initial velocity and coefficients of static and kinetic friction; observe the forces, motion and energy changes
Try this
1. Set both friction coefficients to zero and vary the angle.
2. Add kinetic friction and compare the acceleration.
3. Increase the mass and compare the acceleration.
Look for Acceleration down a slope is g(sin θ − μ cos θ), independent of mass.
Open on The Physics Classroom
Physics Interactives by The Physics Classroom · Licensed to MarkScheme (site terms otherwise permit linking only)

Key formulas

Tap any symbol to reveal exactly what it means and its units.

KEY RELATION

$KE = \frac{1}{2}mv^2$

Tap a symbol — great for exam definitions

KEY RELATION

$GPE = mgh \text{ or } \Delta GPE = mg\Delta h$

Tap a symbol — great for exam definitions

KEY RELATION

= Fd

Tap a symbol — great for exam definitions

KEY RELATION

$W = Fd \cos \theta$

Tap a symbol — great for exam definitions

KEY RELATION

$P = \frac{\Delta E}{\Delta t} \text{ and } P = Fv$

Tap a symbol — great for exam definitions

KEY RELATION

$Efficiency = \frac{\text{Useful Energy Output}}{\text{Total Energy Input}} = \frac{\text{Useful Power Output}}{\text{Total Power Input}}$

Tap a symbol — great for exam definitions

Full topic notes

Formal explanation with the rigour you need for the exam.

The Unbreakable Rule: Conservation of Energy

5.1 Energy conservation.
In physics, work (W) is the energy transferred to or from an object through the application of force (F) along a displacement (d) 𝑊 = 𝐹 × 𝑑.
The SI units for work is in Joules.
The principle of conservation of energy states that energy is neither created nor destroyed. But may transform from one type to another .
E.g. work can be transformed to heat (friction!), electric to light.
Not all energy transferred is useful. E.g. when transferring electric to light, some energy is wasted in the form of heat!.

Not clear?

Energy's Many Forms: Kinetic and Gravitational Potential

$KE = \frac{1}{2}mv^2$

Kinetic energy depends on an object's mass ( $m$ ) and the square of its velocity ( $v$ ). The faster or more massive an object, the more kinetic energy it has.

$GPE = mgh \text{ or } \Delta GPE = mg\Delta h$

Kinetic energy is related to an object's movement.
GPE is energy stored by an object's height in a gravitational field.
KE is proportional to mass and the square of velocity.
GPE depends on mass, gravity, and vertical height change.
The GPE reference height can be set arbitrarily.

Not clear?

Work, Power, and Efficiency: Energy in Action

$W = Fd$

$W = Fd \cos \theta$

Power is how quickly this energy transfer or work happens. A powerful engine can do a lot of work in a short amount of time, indicating a high rate of energy transfer.

$P = \frac{\Delta E}{\Delta t} \text{ and } P = Fv$

$Efficiency = \frac{\text{Useful Energy Output}}{\text{Total Energy Input}} = \frac{\text{Useful Power Output}}{\text{Total Power Input}}$

Work done is energy transferred by a force causing displacement.
Use $W = Fd \cos \theta$ when force and displacement are at an angle $\theta$ .
Power measures the rate of energy transfer or work done.
For constant velocity, power can be calculated as $P = Fv$ .
Efficiency compares useful output energy/power to total input energy/power.
Real systems always have efficiency less than 100% due to energy losses.

Not clear?

Worked examples

See the formulas applied — reveal one step at a time, like the exam.

reveal slowly — mark each step

EXAMPLE 1

1
(a) Initial GPE: $GPE = mgh = 2.0 \text{ kg} \times 9.81 \text{ m/s}^2 \times 5.0 \text{ m} = 98.1 \text{ J}$.

EXAMPLE 2

1
(a) First, find the vertical height gained in 10 seconds.

How it all connects

The big idea sits in the middle — tap a linked idea to explore the link.

MAIN IDEAEnergy conservation

Tap a linked idea to see how it connects back to the main topic — that connection is what examiners reward.

Glossary

Key terms for this topic — skim now; the Check step will test them.

Principle of Conservation of Energy: At its core, the Principle of Conservation of Energy states that energy can neither be created nor destroyed.
Power: Power is how quickly this energy transfer or work happens. A powerful engine can do a lot of work in a short amount of time, indicating a high rate of energy transfer.
Closed system: Energy cannot be created or destroyed, only transformed, so the total energy remains constant.

10Apply

Quick check

Write your answer first, then compare it with the model one — the gap is what you would have lost.

0 of 6 answered

11Understand

Teach it back

If you can explain it simply, you own it — gaps here are marks you’d lose.

Teach it back

Explain this topic as if teaching a friend. We name the gaps an examiner would still dock.

Your explanation — no notes

12Remember

Revision flashcards

Guess first, then flip — retrieval beats re-reading.

Your guess — write it before you look

1 / 15 · ← → space

Key takeaways

Review these before you close the topic — retrieval beats re-reading.

close the tab only after these stick

5.1 Energy conservation.
In physics, work (W) is the energy transferred to or from an object through the application of force (F) along a displacement (d) 𝑊 = 𝐹 × 𝑑.
The SI units for work is in Joules.
The principle of conservation of energy states that energy is neither created nor destroyed. But may transform from one type to another .
E.g. work can be transformed to heat (friction!), electric to light.
Not all energy transferred is useful. E.g. when transferring electric to light, some energy is wasted in the form of heat!.

Practice — then mark it

The whole point: a real Cambridge question, marked mark-by-mark.

Question 1 of 29702/22 · Q3(b)

PhysicsMay/June 2024

(b)

The potential difference between the ground and the atmosphere is 3.0 × 10^7 V.

Calculate the average power, in GW, transferred during the lightning strike.

power = ................................................................ GW

Do it on paper → mark itMARKED MARK-BY-MARK · B1 / M1 / A1 · OFFICIAL SCHEME

9702/22/M/J/24

Question 2 of 29702/23 · Q3(d)

PhysicsMay/June 2024

(d)

Determine an estimate of the work done on the sample as it is extended from zero extension to its breaking point. Explain your reasoning.

Do it on paper → mark itMARKED MARK-BY-MARK · B1 / M1 / A1 · OFFICIAL SCHEME

9702/23/M/J/24

Extra simulations & links

PhET, GeoGebra and other curated tools — open in a new tab.

Frequently asked

Why is it impossible for a machine to be 100% efficient?

When should I use

W = Fd

versus

W = Fd \cos \theta

for work done?

Can gravitational potential energy ever be negative?

Checkpoint

One marked question is worth ten re-reads — close the loop before you move on.

Checkpoint

Reading it isn’t knowing it — prove it.

Before you move on: do 9702/22 · Q3(b) on paper, snap a photo, and get examiner-style feedback on exactly where you win and lose marks.

Attempt & get marked →Takes about a minute · you’ll land back on this lesson

← PREVIOUS4.3 Density and pressure NEXT →5.2 Gravitational potential energy and kinetic energy

Discuss Energy conservation

Ask, share and discuss with other Physics students

Create a post Visit s/9702

Revise Energy conservation for Cambridge 9702 (5.1)

In simple terms

What this topic covers

Explore the concept

Simulations

It's All Uphill

Work-Energy & Friction Floor

Kinetic Energy

CoE on an Inclined Ramp

Chart That Motion

The Ramp

Momentum & Energy: Elastic and Inelastic Collisions

The Ballistic Pendulum

Ballistic Pendulum "Quiz"

Conservation of Mechanical Energy: Mass on a Vertical Spring

Inclined Plane Simulation

Key formulas

Full topic notes

The Unbreakable Rule: Conservation of Energy

Energy's Many Forms: Kinetic and Gravitational Potential

Work, Power, and Efficiency: Energy in Action

Worked examples

How it all connects

Glossary

Quick check

Teach it back

Revision flashcards

Key takeaways

Practice — then mark it

Extra simulations & links

Frequently asked

Checkpoint

Reading it isn’t knowing it — prove it.

Discuss Energy conservation

Revise Energy conservation for Cambridge 9702 (5.1)

In simple terms

What this topic covers

Explore the concept

Simulations

It's All Uphill

Work-Energy & Friction Floor

Kinetic Energy

CoE on an Inclined Ramp

Chart That Motion

The Ramp

Momentum & Energy: Elastic and Inelastic Collisions

The Ballistic Pendulum

Ballistic Pendulum "Quiz"

Conservation of Mechanical Energy: Mass on a Vertical Spring

Inclined Plane Simulation

Key formulas

Full topic notes

The Unbreakable Rule: Conservation of Energy

Energy's Many Forms: Kinetic and Gravitational Potential

Work, Power, and Efficiency: Energy in Action

Worked examples

How it all connects

Glossary

Quick check

Teach it back

Revision flashcards

Key takeaways

Practice — then mark it

Extra simulations & links

Frequently asked

Checkpoint

Reading it isn’t knowing it — prove it.

Discuss Energy conservation