A soldier sits buckled into a seat in a troop transport that is driving down a straight road at 20 m/s. Relative to the transport itself, how is the soldier moving?
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Answer: B
Correct answer: At rest. Motion is always measured relative to a reference point. Inside the transport, the soldier's position does not change, so she is at rest relative to the vehicle, even though both move at 20 m/s relative to the road.
- A: That is the soldier's motion relative to the road, not relative to the vehicle she is riding in.
- B (correct): The soldier keeps the same position inside the transport, so relative to the transport she is not moving.
- C: The road appears to move backward relative to the transport, but the seated soldier does not.
- D: The transport moves at a steady speed in a straight line, and the soldier stays in her seat, so nothing here shows acceleration.