In simple terms
A friendly intro before the formal notes — no formulas yet.
Scalars and vectors
Cambridge 9702 Paper 2 — Scalars and vectors (1.4). Senpai Corner diagram-backed pilot with premium structure and live visuals.
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1.4 Scalars and vectors.
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A scalar is a quantity which only has a magnitude.
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E.g. speed, mass, time and distance.
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A vector is a quantity with both a magnitude and direction.
What this topic covers
The official Cambridge syllabus points this lesson works through.
- 1.4.1
Understand the difference between scalar and vector quantities and give examples of scalar and vector quantities included in the syllabus
- 1.4.2
Add and subtract coplanar vectors
- 1.4.3
Represent a vector as two perpendicular components
Explore the concept
Use the live diagram, PhET or GeoGebra sim, and synced steps — play it, drag controls, or tap a step.
Step-synced diagram — highlights what to look for in the simulation above.
Vectors have magnitude and direction
Vectors have magnitude and direction — show both on diagrams.
26 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.
26 simulations · 5 to start with
Start herein this order — each one shows a different piece of the topic
- oPhysicsStart here · 19702 1.4 · IB A.1 · IB A.2
Vector Addition
Drag the tips of two vectors; see their resultant by triangle or parallelogram method
Why this one: Triangle and parallelogram methods give the same resultant; watch it shrink as the vectors turn antiparallel.
Try this
- Drag the two vector tips so they are perpendicular and read the resultant.
- Switch between the triangle and parallelogram methods for the same pair.
- Drag one tip until the two vectors point the same way.
Look for Both methods give the same resultant; it is longest when the vectors are parallel and shortest when antiparallel.
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 ClassroomStart here · 29702 1.4 · 9702 2.1 · IB A.1
Vector Walk
Three short animated motions; work out the distance travelled and the overall displacement for each
Why this one: Add every step for distance, then draw start-to-finish for displacement: scalar versus vector in one walk.
Try this
- Add up every step of the first motion to get the distance travelled.
- Mark the start and finish and find the overall displacement.
- Repeat for the other two motions and compare the two values each time.
Look for Distance counts every step of the path; displacement is only the straight-line change from start to finish, so it is never larger than distance.
Physics Interactives by The Physics Classroom · Licensed to MarkScheme (site terms otherwise permit linking only)
- oPhysicsStart here · 39702 1.4 · IB A.1 · IB A.2
Vector Components
Enter a vector magnitude and direction; see its x and y components graphically and numerically
Why this one: Enter magnitude and angle, read |v| cos θ and |v| sin θ; past 90° the x-component goes negative.
Try this
- Enter magnitude 10 at 30° and read both components.
- Keep the magnitude and change the direction to 60°, then 90°.
- Enter a direction between 90° and 180° and note the sign of the x component.
Look for The components are |v| cos θ and |v| sin θ, so they swap values between 30° and 60° and the x component turns negative past 90°.
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 ClassroomStart here · 49702 1.4 · IB A.1
Name that Vector
Twelve challenges: add three of the 25 vectors shown on the grid by components and name the resultant
Why this one: Add x-components and y-components separately and name the resultant: the analytical method drilled.
Try this
- Read the x- and y-components of each of the three vectors from the grid.
- Add the x-components and the y-components separately.
- Name the resultant from the two sums and check it.
Look for The components of the resultant are the sums of the x-components and of the y-components.
Physics Interactives by The Physics Classroom · Licensed to MarkScheme (site terms otherwise permit linking only)
- 3JCN PhysicsStart here · 59702 1.4 · IB A.1
Vector Subtraction
Subtract vectors graphically and read the resulting components
Why this one: A minus B is A plus the reversed B: multiplying by −1 flips a vector's direction.
Try this
- Subtract two equal vectors and read the result.
- Reverse the order of subtraction and compare the resulting components.
Look for A minus B equals A plus the reverse of B, so swapping the order reverses the result.
3JCN Physics Simulation by Thomas Nguyen · CC BY 4.0
More simulations21 more on this topic — core ones first
- oPhysicsCore9702 1.4 · IB A.1
Vector Addition and Subtraction
Set magnitude/direction of two vectors with sliders; toggle to show sum or difference vector
Try this
- Set both magnitudes equal and the directions 90° apart; show the sum.
- Toggle to the difference vector without changing the sliders.
- Slide one direction round until the sum is as short as it gets.
Look for The difference A − B is A plus the reversed B, so sum and difference are the two diagonals of the same parallelogram.
Simulation by Tom Walsh, oPhysics.com — made with GeoGebra · Licensed to MarkScheme (site: free for non-profit educational use; applets made with GeoGebra)
- oPhysicsCore9702 1.4 · IB A.1
Vector Addition and Subtraction Practice
Practice worksheet: draw the sum or difference of two given vectors, then check the answer
Try this
- Draw the sum of the two given vectors tip to tail, then check the answer.
- Draw the difference for the same pair and check it.
- Generate a new pair and repeat.
Look for The sum closes the tip-to-tail chain; the difference joins the two tips when the vectors share a tail.
Simulation by Tom Walsh, oPhysics.com — made with GeoGebra · Licensed to MarkScheme (site: free for non-profit educational use; applets made with GeoGebra)
- oPhysicsCore9702 1.4 · 9702 2.1 · IB A.1
Relative Velocity: Boat Crossing a River
Set boat heading, boat speed and river speed; watch the resultant path across the river
Try this
- Point the boat straight across with the river flowing and watch the path.
- Angle the heading upstream until the path is straight across.
- Set the river speed equal to the boat speed and try to cross directly.
Look for The boat’s path follows the vector sum of boat velocity and river velocity, so heading and path differ whenever the river flows.
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 1.4 · IB A.1
Vector Addition
Drag up to three vectors onto the canvas, turn each arrowhead to set its direction, guess the resultant, then tap to draw it
Try this
- Drag two vectors on and guess the direction of the resultant before drawing it.
- Turn one arrowhead to reverse that vector and draw the resultant again.
- Add a third vector and compare the resultant with your guess.
Look for The resultant runs from the tail of the first vector to the head of the last, whatever the arrowheads point.
Physics Interactives by The Physics Classroom · Licensed to MarkScheme (site terms otherwise permit linking only)
- The Physics ClassroomCore9702 1.4 · IB A.1
Vector Walk in Two-Dimensions
Watch a person hike a two-dimensional path, then give the distance and the displacement (magnitude and direction); pass levels to progress
Try this
- Add the lengths of each leg of the hike to get the distance.
- Find the displacement magnitude and direction from start to finish.
- Pass the level and try a hike with more legs.
Look for Distance is the sum of every leg of the hike; displacement is the single vector from start to finish.
Physics Interactives by The Physics Classroom · Licensed to MarkScheme (site terms otherwise permit linking only)
- The Physics ClassroomCore9702 1.4 · 9702 2.1 · IB A.1
The Riverboat Simulator
Cross a river in a boat: set the boat speed, the river speed and the heading, then watch the resulting motion and read the crossing time
Try this
- Set the river speed to zero and read the crossing time.
- Add a river speed and compare the crossing time and the landing point.
- Change the heading and watch where the boat lands.
Look for The river speed adds a velocity component along the bank that leaves the crossing time unchanged.
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.
Tap a symbol — great for exam definitions
Tap a symbol — great for exam definitions
Full topic notes
Formal explanation with the rigour you need for the exam.
Understanding Scalars
A scalar quantity is defined solely by its magnitude – essentially, its size or amount. Scalars have no associated direction. Think of how you measure your mass on a scale; it's just '70 kg', not '70 kg upwards'. These quantities simplify many everyday measurements, focusing only on 'how much'.
1.4 Scalars and vectors.
A scalar is a quantity which only has a magnitude.
E.g. speed, mass, time and distance.
A vector is a quantity with both a magnitude and direction.
Eg. velocity, acceleration, weight, and displacement.
If you want to know if a unit is a scalar or vector try putting a negative in front of it!.
Unveiling Vectors
In contrast, a vector quantity requires both a magnitude and a specific direction to be fully described. For instance, when you talk about your displacement, it's not just '5 meters' but '5 meters North'. Vectors are often represented visually as an arrow; the arrow's length corresponds to the vector's magnitude, and the arrowhead points in its direction.
Defined by magnitude and direction.
Represented by arrows (length = magnitude, arrowhead = direction).
Examples: displacement, velocity, force.
Examples: acceleration, momentum, electric field strength.
Adding Perpendicular Vectors
When two vectors act at right angles (perpendicular) to each other, combining them to find their resultant vector (the single vector equivalent to their combined effect) is straightforward. Imagine two forces, one pulling right and one pulling up. The overall effect, the resultant, can be found using fundamental geometry.
Resultant Magnitude (Pythagoras' Theorem):
Resultant Direction (Trigonometry):
Resolving Vectors
Sometimes, we need to do the reverse of adding: break down a single vector into two components that are at right angles to each other. This process is called vector resolution. It's incredibly useful when a force or velocity acts at an angle, and you need to see its individual effects along, say, horizontal and vertical axes.
If a vector makes an angle with the horizontal (x-axis): Component adjacent to the angle: Component opposite to the angle:
Adding Non-Perpendicular Vectors
When vectors aren't at right angles, you can't use Pythagoras directly. One common and accurate method is to first resolve each vector into its perpendicular components (e.g., horizontal and vertical). Once you have all the horizontal components and all the vertical components, you can add them algebraically to get total horizontal () and total vertical () resultants. Then, combine these two total perpendicular components using Pythagoras' theorem and trigonometry to find the final resultant.
Alternatively, for a more visual approach, you can use scale diagrams and the head-to-tail method. Draw the first vector to scale, then draw the second vector (also to scale) starting from the head (tip) of the first. The resultant is the vector drawn from the tail (start) of the first to the head of the last.
For AS-Level Physics, the analytical method of resolving vectors into components is generally preferred over scale diagrams for accuracy, especially in Paper 2 calculations. Practice both, but master the component method!
Scalar Multiplication of Vectors
Multiplying a vector by a scalar changes its magnitude. If you multiply a vector by a positive scalar, its magnitude changes proportionally, but its direction remains the same. For example, is a vector twice as long as but in the identical direction.
If you multiply a vector by a negative scalar, its magnitude also changes proportionally, but its direction is reversed. So, would be a vector three times the length of but pointing in precisely the opposite direction.
Worked examples
See the formulas applied — reveal one step at a time, like the exam.
A boat is travelling at 3.0 m/s due East, and simultaneously, a current pushes it 4.0 m/s due North. Calculate the magnitude and direction of the boat's resultant velocity.
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Identify components: We have a horizontal velocity component (East) and a vertical velocity component (North). These are perpendicular.
Two forces, N and N, act on a small object P. acts horizontally to the right. acts at an angle of above the horizontal. Calculate the magnitude and direction of the resultant force acting on P.
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Strategy: Resolve each force into horizontal (x) and vertical (y) components. Sum the components, then recombine them to find the resultant. Let's define 'right' and 'up' as positive directions.
How it all connects
The big idea sits in the middle — tap a linked idea to explore the link.
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.
- scalar quantity
A scalar quantity is defined solely by its magnitude – essentially, its size or amount.
- resultant vector
When two vectors act at right angles (perpendicular) to each other, combining them to find their resultant vector (the single vector equivalent to their combined effect) is straightforward.
- vector resolution
This process is called vector resolution. It's incredibly useful when a force or velocity acts at an angle, and you need to see its individual effects along, say, horizontal and vertical axes.
- Resultant Magnitude (Pythagoras' Theorem):
Resultant Magnitude (Pythagoras' Theorem):
- Resultant Direction (Trigonometry):
Resultant Direction (Trigonometry):
- Component adjacent to the angle:
Component adjacent to the angle:
- Component opposite to the angle:
Component opposite to the angle:
Quick check
Write your answer first, then compare it with the model one — the gap is what you would have lost.
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.
Revision flashcards
Guess first, then flip — retrieval beats re-reading.
Key takeaways
Review these before you close the topic — retrieval beats re-reading.
1.4 Scalars and vectors.
A scalar is a quantity which only has a magnitude.
E.g. speed, mass, time and distance.
A vector is a quantity with both a magnitude and direction.
Eg. velocity, acceleration, weight, and displacement.
If you want to know if a unit is a scalar or vector try putting a negative in front of it!.
Practice — then mark it
The whole point: a real Cambridge question, marked mark-by-mark.
Determine the magnitude of the displacement of the object from its original position.
Table 1.1 lists some physical quantities. Identify with ticks (✔) which quantities are vectors and which are scalars.
Extra simulations & links
PhET, GeoGebra and other curated tools — open in a new tab.
Frequently asked
Checkpoint
One marked question is worth ten re-reads — close the loop before you move on.
Reading it isn’t knowing it — prove it.
Before you move on: do 9702/23 · Q2(b)(iv) on paper, snap a photo, and get examiner-style feedback on exactly where you win and lose marks.
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