Intelligent assessment and revision tools for OCR A Physics

On a low-friction track, a 0.50 kg ball moving at +6.0 m s⁻¹ collides head-on with a 1.50 kg cart initially at rest. Two trials are run with identical setup: Trial 1 the ball sticks to the cart; Trial 2 the ball bounces back in a nearly perfectly elastic collision. A force sensor on the cart records the magnitude of the impulse it receives during impact. Which statement must be true about the sensor readings, and why?

• A The impulses are equal in both trials because total momentum before and after is the same.
• B The cart receives a larger impulse when they stick; for these masses it is roughly 3 N s compared with about 2 N s in the elastic bounce.
• C The elastic bounce gives the smaller impulse, since no kinetic energy is lost, so the average force and impulse must be lower.
• D The elastic bounce gives the larger impulse on the cart, about twice that for sticking (roughly 4.5 N s vs 2.25 N s), because the ball reverses direction.