A car moving at 10 m s⁻¹ can be stopped by a constant force F in a distance of 20 m. If the velocity is 30 m s⁻¹, it can be stopped by the same force in:
Options

Question

A car moving at 10 m s⁻¹ can be stopped by a constant force F in a distance of 20 m. If the velocity is 30 m s⁻¹, it can be stopped by the same force in:

G1 Physics · Accepted Answer

With the same constant stopping force, retardation is the same and stopping distance s∝u². Increasing speed from 10 to 30 triples u, so s becomes 9×20=180 m. Hence option D.