Lesson T2.3.2

T2.3.2 Forces and changes in motion Quiz: KS3 Physics, Unit 2

20 questions

Written by Revision Ninja · Last reviewed 11 October 2026

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Lesson T2.3.2, Forces and changes in motion: 20 multiple choice questions for the KS3 Physics (National Curriculum), Unit 2: Motion and forces, written with Revision Ninja.

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The 20 questions

  1. What must act on a stationary object for it to start moving?

    • An unbalanced force
    • A force of zero size applied to the centre of the object, which keeps it in place
    • No force at all, because objects move naturally without any push or pull being applied
    • A balanced force of equal size acting in both directions along the same straight line

  2. Forces can change an object's motion by changing which two things?

    • Its speed or its direction of motion
    • Its mass or its density, which are both properties of the material the object is made from
    • Its colour or its temperature, which can both be altered by a sufficiently strong force
    • Its electric charge or its resistance, which are both changed by any force acting on it

  3. A cyclist brakes to slow down. Which force slows the bicycle?

    • Kinetic energy of the cyclist pushing the bike forwards, which works against the brakes
    • The weight of the bicycle acting upwards, which lifts the wheels off the road as it slows
    • Friction between the brake pads and the wheel
    • A forward force from the road pushing the bike ahead, which helps the cyclist stop safely

  4. A parachutist falls at a steady speed. Why is her speed constant?

    • Air pushes her downwards with an extra force, which keeps her moving at a steady speed.
    • The parachute has no mass, so no force from gravity or the air acts on the whole system.
    • Her weight becomes zero while she is in the air, so gravity no longer pulls her down at all.
    • Air resistance balances her weight, so the resultant force is zero.

  5. A football is kicked along the grass and slows down. Which force causes it to slow?

    • The ball's own momentum pushing it forward, which gradually runs out as it rolls
    • Friction and air resistance acting against its motion
    • Upthrust from the grass pushing it forwards, which lifts the ball and pushes it along
    • A forward force from the kick that never stops acting on the ball as it rolls along

  6. What does it mean to say that forces are vectors?

    • They have a size but no direction, so they can be added in any order without a sign.
    • They have a colour and a mass, so they can be drawn on a diagram as coloured arrows.
    • They have a direction but no size, so they can only be shown as arrows of equal length.
    • They have both a size and a direction.

  7. A trolley is pushed to the right with a 10 N force while 4 N of friction acts to the left. What happens to its speed?

    • It stays at the same speed, because the push and the friction are roughly equal in size.
    • It slows down, opposite to the push, because the friction is the larger of the two forces.
    • It stops immediately, because the friction acts on the trolley with a force greater than the push.
    • It speeds up in the direction of the push.

  8. Which force resists the motion of an object moving through water?

    • Atmospheric pressure acting on the surface of the water, which pushes the object down
    • Static electricity between the object and the water, which builds up as it moves through
    • Water resistance, also called drag
    • Gravity pulling the object towards the Earth, which acts on it wherever it is located

  9. Why is it harder to ride a bicycle into a strong headwind?

    • Air resistance acts against the motion, so a bigger force is needed to keep the same speed.
    • The wind removes the cyclist's weight entirely, which makes pedalling harder to manage.
    • Air pushes the cyclist sideways rather than backwards, which slows the bicycle down as it turns.
    • Wind has no effect on the forces acting on a moving cyclist, so the extra effort must come from fatigue.

  10. Why does a falling object eventually stop speeding up?

    • Air resistance grows until it balances the weight, giving zero resultant force.
    • Its mass becomes smaller every second it falls, so it accelerates less as it goes lower.
    • Gravity switches off at a fixed speed, so the object carries on falling at a constant rate.
    • Its weight decreases as it falls, so gravity pulls it down with less and less force each second.

  11. What is friction?

    • A force between surfaces at a distance from each other that helps their motion along.
    • A force between surfaces in contact that opposes their motion.
    • A force that acts only on objects that are completely still and not moving at all.
    • A force that acts only inside liquids and never on solid objects that touch each other.

  12. What is an unbalanced force?

    • A pair of forces that always cancel out to give exactly zero resultant force on the object.
    • Two equal forces that push on the same point of an object from opposite sides at once.
    • A force combination that does not cancel out, so the resultant force is not zero.
    • A single force that acts on an object which is not moving at the time it is applied.

  13. What is needed to change the direction of a moving ball?

    • A force only at the moment the ball comes to a stop, which then sends it off again
    • A balanced force acting in the same direction as its motion, which speeds the ball up
    • No force at all, because a moving ball keeps its direction on its own without help
    • An unbalanced force acting at an angle to its motion

  14. Why are streamlined shapes used for cars, planes and boats?

    • They reduce the weight of the object, so less force is needed from the engine to move it.
    • They reduce the mass of the object, which makes it easier to accelerate from rest.
    • They keep the object at a lower temperature, which stops its materials from wearing out.
    • They reduce air or water resistance on the moving object.

  15. Two forces of 15 N and 9 N act on a box in opposite directions. The box starts at rest. What happens?

    • The resultant is 24 N in the direction of the 15 N force, so the box speeds up sharply.
    • The resultant is 0 N, so the box stays at rest because the two forces cancel each other.
    • The resultant is 6 N in the direction of the 9 N force, so the box accelerates that way.
    • The resultant is 6 N in the direction of the 15 N force, so the box accelerates that way.

  16. Which example shows a force changing an object's shape rather than its motion?

    • Kicking a stationary football into the air, which changes the ball's speed and direction
    • Squeezing a rubber ball so that it bulges
    • Braking a bicycle until it stops, which changes the bicycle's speed to zero on the road
    • Pushing a trolley along a flat track, which changes the trolley's position along the track

  17. A swimmer pushes water backwards with their hands and legs. What forward force results?

    • The reaction push from the water, acting forwards on the swimmer
    • Atmospheric pressure pushing from above, which squeezes the swimmer forwards through the water
    • Gravity pulling the swimmer forwards along the pool, which keeps them moving along it
    • Upthrust from the floor of the pool, which lifts the swimmer and pushes them ahead

  18. A moving trolley is pushed with a 20 N force while 12 N of friction acts against it. Which way does its speed change?

    • It keeps the same speed, because the push and the friction together make the forces balanced.
    • It speeds up in the direction of the push.
    • It slows down, opposite to the push, because the friction is the larger of the two forces here.
    • It stops immediately, because the friction removes all of the push force in a single moment.

  19. Which statement about changing velocity is correct?

    • Direction can change without any force acting on the object, because objects turn by themselves.
    • Velocity changes only when an object becomes heavier, since extra mass is what changes its motion.
    • Speed can only change if no forces act on the object, because forces always keep speed the same.
    • A change in velocity needs a resultant force, even when the speed stays the same.

  20. Why does a faster car need a greater braking force to stop in the same distance as a slower car?

    • The faster car has less mass, so it needs less braking force to stop within the same distance.
    • The faster car has more motion to remove, so a bigger force is needed in the same distance.
    • Faster cars are not affected by friction at the brakes, so they need no extra force to stop.
    • Speed has no effect on the braking force needed to stop a car, because only mass matters here.

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