A small glider moves along a horizontal air track as shown.
At each end of the air track, the glider has a perfectly elastic collision with a fixed buffer.
The glider moves at a constant speed between collisions.
Which graph represents the variation with time t of the velocity v of the glider as it moves between the two buffers?
ANSWER: D
The Physics behind the answer:
- By "has a perfectly elastic collision" it means that the kinetic energy of the glider is conserved.
- This means further that, for each collision, the speed of the glider remains the same.
- It is only the direction of the glider that changes at every collision.
- Since the options A, B, C and D are all velocity-time graph i.e. speed plus the directions, following the Cartesian plane conventions it is D that tells that speed [or magnitude of velocity] doesn't change while directions do every collision with the fixed buffers.
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