Name three scalar quantities.

Distance, speed and mass (also time and energy).

Name three vector quantities.

Displacement, velocity and force (also weight and acceleration).

What is the difference between distance and displacement?

Distance is the total path length. Displacement is the straight-line distance from start to finish, with direction.

What is the difference between mass and weight?

Mass is the amount of matter (kg, scalar). Weight is the force of gravity on it (N, vector, acts downwards).

How do you find the resultant of two forces acting in opposite directions?

Subtract the smaller from the larger; the resultant acts in the direction of the larger force.

What does it mean if forces are balanced?

The resultant force is zero, so there is no change in velocity.

What happens to an object when the forces on it are unbalanced?

It accelerates in the direction of the resultant force.

How do you find the resultant of two perpendicular forces by calculation?

Use Pythagoras: R = √(F₁² + F₂²).

What is the resultant of perpendicular forces of 6 N and 8 N?

10 N, since √(36 + 64) = √100.

What are the steps of a scale drawing for two perpendicular forces?

Choose a scale, draw the forces at 90° tip to tail, draw the resultant from start to end, measure it and convert with the scale.

What does equilibrium mean?

The forces on the object are balanced, so the resultant is zero.

Resultant force and vectorsIB MYP Physics: Flashcards

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What is the difference between a scalar and a vector?

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What is the difference between a scalar and a vector?: A scalar has size only; a vector has size and direction.
Name three scalar quantities.: Distance, speed and mass (also time and energy).
Name three vector quantities.: Displacement, velocity and force (also weight and acceleration).
What is the difference between distance and displacement?: Distance is the total path length. Displacement is the straight-line distance from start to finish, with direction.
What is the difference between mass and weight?: Mass is the amount of matter (kg, scalar). Weight is the force of gravity on it (N, vector, acts downwards).
How do you find the resultant of two forces acting in opposite directions?: Subtract the smaller from the larger; the resultant acts in the direction of the larger force.
What is the resultant of 12 N right and 5 N left?: 7 N to the right.
What does it mean if forces are balanced?: The resultant force is zero, so there is no change in velocity.
What happens to an object when the forces on it are unbalanced?: It accelerates in the direction of the resultant force.
How do you find the resultant of two perpendicular forces by calculation?: Use Pythagoras: R = √(F₁² + F₂²).
What is the resultant of perpendicular forces of 6 N and 8 N?: 10 N, since √(36 + 64) = √100.
What are the steps of a scale drawing for two perpendicular forces?: Choose a scale, draw the forces at 90° tip to tail, draw the resultant from start to end, measure it and convert with the scale.
What does equilibrium mean?: The forces on the object are balanced, so the resultant is zero.

Exam questions on Resultant force and vectors

A delivery cyclist in Nairobi rides 6 km east along a straight road, then turns and rides 8 km north to reach a school. The whole journey takes 40 minutes.
Explain why the size of the cyclist's displacement is different from the distance she travels.2 marks
Two workers in a warehouse in Lagos push a heavy crate along a smooth floor. Friction between the crate and the floor is so small that it can be ignored. One worker pushes to the right with a force of 300 N and the other pushes to the left with a force of 220 N.
A third worker joins and also pushes to the left, with a force of 80 N. The crate is moving to the right at that moment. Calculate the new resultant force and describe how the crate's motion now changes.2 marks
A student in Seoul is finding out how two forces at right angles combine. She fixes a small metal ring to a flat board. Two newton meters pull the ring at right angles to each other, and a third newton meter pulls in the opposite direction to the resultant of the first two so that the ring stays at rest.
She pulls the ring with forces of 6.0 N and 8.0 N at right angles to each other. Calculate the reading on the third newton meter when the ring is at rest.3 marks

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Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).