m g down
mu m g friction force
F = m a
mu m g = m a
a = mu g = .4 (9.81) = 3.92 m/s^2
a = change in speed/time
change in speed = v
average speed during stop = v/2
distance = average speed * time
5 meters = v/2 t
so
t = 10/v
a = v /(10/v) = v^2/10
so
v^2/10 = 3.92
v^2 = 39.2
v = 6.26 m/s
A 0.80 10^3 kg Toyota collides into the rear end of a 2.6 1^03 kg Cadillac stopped at a red light. The bumpers lock, the brakes are locked, and the two cars skid forward 5.0 m before stopping. The police officer, knowing that the coefficient of kinetic friction between tires and road is 0.40, calculates the speed of the Toyota at impact. What is that speed?
1 answer
1 answer