A long passenger train moves at an unknown speed along straight tracks

PHYSICS · Single correct · AP · Physics 1: Algebra-based · Kinematics · Kinematics

Problem

A long passenger train moves at an unknown speed along straight tracks. A passenger on the train measures Car X, traveling on a nearby road, to move 15 m/s east relative to the train. The same passenger measures Car Y on the road to move 25 m/s west relative to the train. A roadside traffic camera fixed to Earth records Car X at 5 m/s east and Car Y at 35 m/s west, both relative to the ground. What is the train’s velocity relative to the ground? (a) 20 m/s west20\ \text{m/s west} (b) 10 m/s east10\ \text{m/s east} (c) 10 m/s west10\ \text{m/s west} (d) 20 m/s east20\ \text{m/s east}

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