Question

At an accident scene on a level road, investigators measure a car's skid mark to be 78 m long. It was a rainy day, so the coefficient of friction was estimated to be 0.30. Use this data to determine the speed of the car (in m/s) when the driver slammed on the brakes?

Answer 1

KE=1/2 mv² = FD

where FD =umgd , thus,

1/2mv²= umgd

1/2v² =ugd

v² = 2 ugd

v =√2ugd

v=√2(0.3)(9.81)(78)

v=21.4m/s