# A driver in a 1000.0 kg car traveling at 20 m/s slams on the brakes and skids to a stop. If the coefficient of friction between the tires and the road is 0.80, how long will the skid marks...

A driver in a 1000.0 kg car traveling at 20 m/s slams on the brakes and skids to a stop. If the coefficient of friction between the tires and the

road is 0.80, how long will the skid marks be?

A) 26 m

B) 21 m

C) 33 m

D) 24 m

### 1 Answer | Add Yours

Using F = ma to the direction of travel;

`-F = 1000*a`

-F is due to the reverse direction of the frictional force.

`F = 0.8*1000*9.81 = 7850 N`

`-7850 = 1000*a`

`a = -7.85m/s^2`

Using `V^2 = U^2+2aS` to the direction of travel

`0 = 20^2+2*(-7.85)S`

`S = 25.5 m`

*So the skid marks will be there for 25.5m `~~` 26m.*

*The correct answer is A).*

**Sources:**