A-LevelPhysicsDynamics9702/12 · May/June 2025 · Q131 Mark
An empty cart is moving along a horizontal track at a constant velocity. Resistive forces acting on the cart are negligible. A heavy rock is dropped vertically into the cart. [Diagram shows a cart moving right, with a rock falling vertically into it.] The cart continues to move horizontally with the rock inside. How does the momentum and kinetic energy of the cart with the rock inside compare with the momentum and kinetic energy of the empty cart?
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AThe cart with the rock inside has a smaller momentum and a smaller kinetic energy.
BThe cart with the rock inside has a smaller momentum and the same kinetic energy.
CThe cart with the rock inside has the same momentum and a smaller kinetic energy.
DThe cart with the rock inside has the same momentum and the same kinetic energy.
✓ Correct answer
C: The cart with the rock inside has the same momentum and a smaller kinetic energy.
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