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    Momentum Calculator (p = mv)

    GCSE PhysicsAQAEdexcelOCRHigher tier

    Find momentum, mass or velocity using p = m × v. Enter grams, tonnes or km/h and the solver converts to SI units.

    Quick answer

    Momentum = mass × velocity. Use kg and m/s to get kg m/s. For example, a 0.16 kg ball at 25 m/s has a momentum of 0.16 × 25 = 4.0 kg m/s. In a closed system, total momentum is conserved.

    By Engr. Mehmood Kakar · Updated

    p = m × v
    Find:

    Simulation

    Momentum is conserved

    Trolley A moves with momentum p = mv and hits trolley B, which is at rest. They stick together: the total momentum is the same before and after.

    2 kg
    3 m/s
    1 kg

    In a closed system, total momentum before = total momentum after. Heavier combined mass means a lower speed afterwards.

    Put these numbers in the calculator above

    How to calculate momentum

    Momentum is a property of moving objects. It depends on mass and velocity:

    momentum = mass × velocity

    • p is momentum in kilogram metres per second (kg m/s)
    • m is mass in kilograms (kg)
    • v is velocity in metres per second (m/s)

    A 0.16 kg cricket ball moving at 25 m/s has a momentum of 0.16 × 25 = 4.0 kg m/s.

    Momentum is a vector, so its direction matters: objects moving in opposite directions have momentum of opposite signs. In a closed system, the total momentum before an event (such as a collision or explosion) equals the total momentum after it. This is conservation of momentum.

    In AQA GCSE Physics and Combined Science, momentum calculations are Higher tier.

    Common mistakes that cost marks

    1. Leaving mass in grams. 160 g is 0.16 kg.
    2. Not converting km/h. 72 km/h is 20 m/s.
    3. Getting the unit wrong. Momentum is in kg m/s, not N or J.
    4. Ignoring direction in collisions. Give momentum in the opposite direction a negative sign.

    Practice questions

    Try each one on paper first, then reveal the worked answer.

    Q1A 0.16 kg cricket ball moves at 25 m/s. Calculate its momentum.[2 marks]
    1. p = m × v
    2. p = 0.16 × 25
    3. p = 4.0 kg m/s
    Q2A car moving at 20 m/s has a momentum of 24,000 kg m/s. Calculate its mass.[3 marks]
    1. Rearrange: m = p ÷ v
    2. m = 24,000 ÷ 20
    3. m = 1200 kg
    Q3A 70 kg skater has a momentum of 560 kg m/s. Calculate her velocity.[3 marks]
    1. Rearrange: v = p ÷ m
    2. v = 560 ÷ 70
    3. v = 8.0 m/s

    Endless practice

    A new question every time, marked instantly. Work it out on paper, then type your answer.

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    Frequently asked questions

    What is the equation for momentum?

    Momentum = mass × velocity (p = mv). Momentum is in kg m/s, mass in kg and velocity in m/s.

    What is conservation of momentum?

    In a closed system, the total momentum before an event is equal to the total momentum after the event.

    Is momentum a vector?

    Yes. It has both size and direction, the same direction as the velocity.

    Is momentum Higher tier?

    Yes. In AQA GCSE Physics and Combined Science, momentum is Higher tier content.