A trolley moves away from a stop with acceleration 0.2 m s⁻². After reaching 36 km h⁻¹, it moves at constant velocity for 2 min, then uniformly slows and stops after a further 100 m. Find the average speed between stops.
Options

Question

A trolley moves away from a stop with acceleration 0.2 m s⁻². After reaching 36 km h⁻¹, it moves at constant velocity for 2 min, then uniformly slows and stops after a further 100 m. Find the average speed between stops.

Options

G1 Physics · Accepted Answer

Acceleration phase: from rest to 10 m s⁻¹ at 0.2 m s⁻² takes 50 s and covers 250 m. Uniform phase: 10×120=1200 m. Final stopping distance is 100 m; with uniform retardation, stopping time =2s/v=20 s. Total distance=1550 m, total time=190 s. Average speed=1550/190=155/19 m s⁻¹. Hence option D.