Momentum in two dimensions and collisionsEdexcel International A Level Physics: Subtopic test

1. 1
   On a frictionless air table a puck of mass 0.16 kg moving at 5.0 m s⁻¹ collides with an identical stationary puck. After the collision the first puck moves at 3.0 m s⁻¹ at 53° to its original direction of motion, and the second puck moves off on the other side of the original line of motion.

   (a)

   What is the component of momentum of the second puck perpendicular to the original direction of motion?

   [1 mark]

   • A0.38 kg m s⁻¹, on the opposite side of the original line to the first puck
   • B0.38 kg m s⁻¹, on the same side of the original line as the first puck
   • C0.48 kg m s⁻¹, on the opposite side of the original line to the first puck
   • DZero

   (b)

   What is the speed of the second puck after the collision?

   [1 mark]

   • A2.0 m s⁻¹
   • B3.0 m s⁻¹
   • C4.0 m s⁻¹
   • D5.0 m s⁻¹

   (c)

   Determine whether the collision is elastic.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A spring-loaded plunger gives each of two trolleys, X of mass 0.50 kg and Y of mass 2.0 kg, a momentum of 3.0 kg m s⁻¹ along a frictionless track.

   (a)

   What is the speed of trolley Y after the plunger acts?

   [1 mark]

   • A6.0 m s⁻¹
   • B3.0 m s⁻¹
   • C0.67 m s⁻¹
   • D1.5 m s⁻¹

   (b)

   What is the kinetic energy of trolley X?

   [1 mark]

   • A4.5 J
   • B9.0 J
   • C18 J
   • D2.25 J

   (c)

   Derive an expression for the kinetic energy of a non-relativistic particle in terms of its momentum p and mass m, and use it to calculate the kinetic energy of trolley Y.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   In Core Practical 10 a student films a ball bearing of mass 0.028 kg moving at 0.60 m s⁻¹ across a smooth table top as it collides with an identical stationary ball bearing, and uses video analysis software to measure the motion. After the collision the first ball bearing moves at 0.30 m s⁻¹ at 40° to its original direction, and the second moves off on the other side of the original line of motion.

   (a)

   Calculate the speed and direction of motion of the second ball bearing after the collision.

   [3 marks]

   (b)

   Determine whether the collision is elastic or inelastic, and suggest what happened to any kinetic energy that was lost.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   At a junction a car of mass 1200 kg travelling east at 15 m s⁻¹ collides with a van of mass 1800 kg travelling north at 10 m s⁻¹. The two vehicles lock together and move off as one wreck. Friction with the road during the impact is negligible compared with the collision forces.

   (a)

   Calculate the speed and direction of the wreck immediately after the collision, explaining how conservation of momentum is applied.

   [6 marks]

   (b)

   Use Ek = p²/2m to determine whether the collision is elastic or inelastic, and calculate the kinetic energy lost.

   [6 marks]

   Total for question 4: 12 marks

End of questions