Lesson 6.1.2

6.1.2 Conservation of momentum in two dimensions Quiz: Pearson Edexcel Physics, Unit 6

20 questions

Written by Revision Ninja · Last reviewed 11 October 2026

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Lesson 6.1.2, Conservation of momentum in two dimensions: 20 multiple choice questions for the Pearson Edexcel Physics (9PH0), Unit 6: Further Mechanics, written with Revision Ninja.

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The 20 questions

  1. In a two-dimensional collision with no net external force, which quantity is conserved?

    • The total linear momentum of the system, applied separately to each perpendicular direction
    • The speed of each particle, applied separately to each perpendicular direction
    • The total kinetic energy of the system, applied separately to each perpendicular direction
    • The total mass of the system, applied separately to each perpendicular direction

  2. Why is the total momentum of an isolated system unchanged by a collision?

    • There is no net external force acting on the system
    • Every particle keeps the same speed throughout the collision
    • The masses of the particles never change during the collision
    • The collision is always perfectly elastic

  3. Momentum is a vector quantity. Which statement about it is correct?

    • It has a magnitude and a direction, and its direction is the same as the direction of the velocity
    • It has a magnitude and a direction, and its direction is always perpendicular to the velocity
    • It is a scalar quantity, so it can be added to other momenta without regard to direction
    • It has a magnitude only, and its direction is always opposite to the velocity

  4. A two-dimensional problem is solved by resolving momenta into components. What is the correct procedure?

    • Apply conservation of momentum only along the line of the initial velocity and ignore the perpendicular components
    • Add the magnitudes of all the momenta and apply conservation of momentum to that single total
    • Find the kinetic energy of each particle and apply conservation of energy in one direction only
    • Resolve each momentum into two perpendicular components, then apply conservation of momentum separately in each direction

  5. Two 0.50 kg balls collide. Ball A moves east at 3.0 m s^-1 and ball B is at rest. After the collision A moves at 2.0 m s^-1 at 30 degrees north of east and B moves south of east. What is the speed of B?

    • 2.5 m s^-1
    • 3.0 m s^-1
    • 1.0 m s^-1
    • 1.6 m s^-1

  6. A 2.0 kg object at rest explodes into a 0.5 kg piece moving north at 6.0 m s^-1 and a 1.5 kg piece. What is the velocity of the 1.5 kg piece?

    • 2.0 m s^-1 south
    • 6.0 m s^-1 south
    • 4.0 m s^-1 south
    • 2.0 m s^-1 north

  7. A 2.0 kg trolley moving east at 3.0 m s^-1 collides with and sticks to a 1.0 kg trolley moving north at 6.0 m s^-1. What is the velocity of the combined mass?

    • 2.0 m s^-1 at 30 degrees north of east
    • 6.0 m s^-1 at 45 degrees north of east
    • 2.8 m s^-1 at 45 degrees north of east
    • 4.2 m s^-1 at 45 degrees north of east

  8. A 0.40 kg ball moves at 5.0 m s^-1 at 60 degrees to the x-axis. What is the x-component of its momentum?

    • 1.0 kg m s^-1
    • 2.0 kg m s^-1
    • 3.5 kg m s^-1
    • 1.7 kg m s^-1

  9. A 1500 kg car moves north at 10 m s^-1 and a 1000 kg van moves east at 12 m s^-1. They collide and stick together. What is the speed of the wreckage immediately afterwards?

    • 2.5 m s^-1
    • 12 m s^-1
    • 5.0 m s^-1
    • 7.7 m s^-1

  10. Using the same car and van collision, what is the direction of the wreckage's velocity?

    • About 39 degrees north of east
    • About 45 degrees north of east
    • About 51 degrees north of east
    • About 63 degrees north of east

  11. A 0.010 kg bullet travelling at 400 m s^-1 embeds itself in a 2.0 kg block initially at rest on a smooth surface. What is the speed of the block and bullet immediately afterwards?

    • 2.0 m s^-1
    • 400 m s^-1
    • 4.0 m s^-1
    • 0.20 m s^-1

  12. Two identical smooth spheres collide elastically in two dimensions. One is initially at rest and the collision is not head-on. What is the angle between their velocities after the collision?

    • 45 degrees
    • 90 degrees
    • 60 degrees
    • 180 degrees

  13. A stationary 3.0 kg object explodes into a 1.0 kg piece moving east at 6.0 m s^-1 and a second piece. What is the velocity of the second piece?

    • 2.0 m s^-1 west
    • 3.0 m s^-1 west
    • 6.0 m s^-1 west
    • 6.0 m s^-1 east

  14. A 0.20 kg ball moves east at 5.0 m s^-1 and collides with a 0.30 kg ball moving north at 4.0 m s^-1. They stick together. What is the speed of the combined mass?

    • 5.0 m s^-1
    • 3.1 m s^-1
    • 1.6 m s^-1
    • 4.4 m s^-1

  15. For the ball collision in the previous case, at what angle to east does the combined mass move?

    • About 30 degrees north of east
    • About 40 degrees north of east
    • About 50 degrees north of east
    • About 60 degrees north of east

  16. A student claims that kinetic energy must be conserved in every two-dimensional collision because momentum is conserved. Which response is correct?

    • The claim is correct: momentum conservation in each direction always forces kinetic energy to be conserved
    • The claim is wrong: momentum conservation does not imply kinetic energy conservation, which holds only for elastic collisions
    • The claim is wrong because kinetic energy is a vector quantity that cannot be conserved in two dimensions
    • The claim is correct, but only when the two particles have equal masses and equal speeds

  17. A 0.50 kg ball moving east at 4.0 m s^-1 hits a 1.0 kg ball at rest. The first ball leaves at 2.0 m s^-1 at 60 degrees to east, northwards. What is the speed of the 1.0 kg ball?

    • 1.0 m s^-1
    • 2.6 m s^-1
    • 2.0 m s^-1
    • 1.7 m s^-1

  18. Using the same collision, at what angle to the east does the 1.0 kg ball move?

    • 60 degrees north of east
    • 30 degrees south of east
    • 30 degrees north of east
    • 60 degrees south of east

  19. Two perfectly inelastic collisions involve equal masses m, moving at 3.0 m s^-1 each at right angles to one another. What is the speed of the combined mass?

    • 1.5 m s^-1
    • 2.1 m s^-1
    • 3.0 m s^-1
    • 4.2 m s^-1

  20. Which statement is correct about a two-dimensional collision between two particles with no net external force?

    • The velocity of each particle is the same before and after the collision
    • The sum of the speeds of the particles is the same before and after the collision
    • The vector sum of the momenta is the same before and after the collision
    • The kinetic energy of the particles is the same before and after the collision

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