Physics (AS & A Level) · May / June 2019 · Paper 12 · Question 11

Two bar magnets P and Q are mounted on floats which can slide without friction along an air track. The two magnets slide towards each other along the air track and interact, without making contact. The relative speed of approach of the magnets is equal to their relative speed of separation. Which statement about P and Q must be correct?

1. ADuring the interaction between P and Q some of the total kinetic energy is lost.
2. BDuring the interaction between P and Q some of the total momentum is lost.
3. CThe momentum of Q after the interaction is equal to the momentum of P before the interaction.
4. DThe values of (kinetic energy of P + kinetic energy of Q) before and after the interaction are equal.

As printed in the paper