AQA GCSE Physics
AQA GCSE Physics 4.5.7 Momentum Exam Questions
Free AQA GCSE Physics exam questions for 4.5.7 Momentum, with a mark scheme for every pack. Covers momentum, p = mv, conservation of momentum in collisions and explosions, rate of change of momentum, and safety features.
4.5.7 Momentum exam questions
2 question packs of real past exam questions, each with its mark scheme. Do not stop after a few: answer as many as you can without notes, then mark every answer with the mark scheme. The more questions you do, the more quickly you will spot how examiners ask about each idea.
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About AQA GCSE Physics 4.5.7 Momentum
Momentum is Higher tier only content in AQA GCSE Physics, examined on Paper 2. You need p = m v, the conservation of momentum in closed systems such as collisions and explosions, and (physics only) the link between force and the rate of change of momentum. That last idea explains how car safety features such as airbags, seat belts, crumple zones and cushioned surfaces reduce injury by increasing the time taken for the change in momentum. Examiners set conservation calculations, often with objects moving in opposite directions, and six-mark safety explanations.
What you need to know
- Momentum (Higher tier only) Momentum is a property of moving objects. p = m v, where p is momentum in kg m/s, m is mass in kg and v is velocity in m/s. This must be memorised. Momentum is a vector.
- Conservation of momentum (Higher tier only) In a closed system, the total momentum before an event is equal to the total momentum after the event. This is called conservation of momentum.
- Collisions and explosions (Higher tier only) Use conservation of momentum to calculate velocities after collisions (such as two trolleys sticking together) and explosions (such as a gun recoiling). In an explosion from rest the total momentum is zero before and after.
- Force and change in momentum (physics only, Higher tier only) When a force acts on an object that is moving, or able to move, a change in momentum occurs. F = m Δv / Δt, so force equals the rate of change of momentum. This equation is on the equation sheet.
- Safety features (physics only, Higher tier only) Air bags, seat belts, gymnasium crash mats, cycle helmets and cushioned playground surfaces increase the time taken for the change in momentum, which reduces the rate of change of momentum and so reduces the force on the person.
- Direction Because momentum is a vector, choose a positive direction. Momentum in the opposite direction is negative.
Common mistakes in 4.5.7 Momentum
- Ignoring direction in collisions. Objects moving in opposite directions have momenta of opposite sign.
- Saying safety features reduce the change in momentum. The change in momentum is the same; the time is longer, so the force is smaller.
- Using kinetic energy conservation instead of momentum. Momentum is always conserved in a closed system; kinetic energy usually is not.
- Giving momentum units of kg/m s or N. The unit is kg m/s.
Try three 4.5.7 Momentum exam-style questions
1. Higher tier: Calculate the momentum of a 0.16 kg ball moving at 25 m/s. (2 marks)
Show the mark scheme answer
p = m v = 0.16 x 25; = 4.0 kg m/s.
2. Higher tier: A 2.0 kg trolley moving at 3.0 m/s collides with a stationary 1.0 kg trolley and they stick together. Calculate their velocity after the collision. (3 marks)
Show the mark scheme answer
Momentum before = 2.0 x 3.0 = 6.0 kg m/s; after: 6.0 = 3.0 x v; v = 2.0 m/s.
3. Physics only, Higher tier: Explain how an airbag reduces the risk of injury to a driver in a crash. (4 marks)
Show the mark scheme answer
The driver's momentum changes from a large value to zero in the crash; the airbag increases the time taken for this change in momentum; so the rate of change of momentum is smaller; force = rate of change of momentum, so the force on the driver is smaller.
4.5.7 Momentum FAQs
What does AQA GCSE Physics 4.5.7 Momentum cover?
It covers p = m v, conservation of momentum in collisions and explosions and, for physics, force as rate of change of momentum and how safety features reduce forces.
Is momentum Higher tier only?
Yes, all of 4.5.7 is Higher tier only. The section on changes in momentum and safety features is also physics only.
What equations do I need for momentum?
Memorise p = m v. The equation F = m Δv / Δt is on the equation sheet. Always state your chosen positive direction.
