Calculate the coefficient of kinetic friction for a 1,500 kg car moving at 62 km/h that skids 18 m to rest when its brakes are locked. Speed must be in m/s.

0.84

Explanation:

First, convert km/h to m/s.

62 km/h * (1000 m / km) * (1 h / 3600 s) = 17.2 m/s

Next, find the acceleration.

v² = v₀² + 2aΔx

(0 m/s) ² = (17.2 m/s) ² + 2a (18 m)

a = - 8.24 m/s²

Now, find the friction force.

∑F = ma

-F = (1500 kg) (-8.24 m/s²)

F = 12,400 N

On a level surface, normal force equals the weight.

N = mg

N = (1500 kg) (9.8 m/s²)

N = 14,700 N

The coefficient of kinetic friction is therefore:

μ = F / N

μ = 12,400 N / 14,700 N

μ = 0.841

Rounding to two significant figures, the coefficient of kinetic friction is 0.84.