Question

A 2600 kg truck travelling at 72 km/h slams on the brakes and skids to a stop. The frictional force from the road is 8200 N. Use the relationship between kinetic energy and mechanical work to determine the distance it takes for the truck to stop.

Answer 1

kinetic energy of truck equals the work done to stop

there are 3600 seconds in an hour ... 60 min/hr * 60 sec/min

72000 m/hr / 3600 sec/hr = 20 m/s

1/2 m v^2 = f d ... 1/2 * 2600 kg * (20 m/s)^2 = 8200 N * d

solve for d (the stopping distance in meters)