A train moves uniformly east. A car moves with constant speed on a road initially parallel to the track and later perpendicular to it. The car driver observes the train's relative speed to be 7 m s⁻¹ initially and 13 m s⁻¹ later. Which values can be the true speed of the car?
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Question

A train moves uniformly east. A car moves with constant speed on a road initially parallel to the track and later perpendicular to it. The car driver observes the train's relative speed to be 7 m s⁻¹ initially and 13 m s⁻¹ later. Which values can be the true speed of the car?

Select all that apply

G1 Physics · Accepted Answer

Let train speed be V and car speed u. Initially |V-u|=7. Later √(V²+u²)=13. Solving gives u=5 m s⁻¹ or 12 m s⁻¹. Hence A,B.