Determine the average frictional force required to bring a car weighing 500 kg to a halt over a distance of 25 m , given that its initial speed is 72 km/h .

Step-by-step solution

Initial velocity u = 72 km/h = 72 5 18 m/s = 20 m/s Final velocity v = 0 Distance s = 25 m Mass m = 500 kg Using the work-energy theorem: Work done by friction = Change in kinetic energy -F s = 1 2 mv^2 - 1 2 mu^2 -F 25 = 0 - 1 2 500 (20)^2 -25F = -250 400 25F = 100000 F = 4000 N