#### Question

# Help please! A car is traveling at 53.0 km/h on a flat highway.?

A car is traveling at 53.0 km/h on a flat highway.

a) If the coefficient of friction between road and tires on a rainy day is 0.100, what is the minimum distance in which the car will stop?

______m

(b) What is the stopping distance when the surface is dry and the coefficient of friction is 0.600?

______m

#### Answer

we can use

vf^2=v0^2 + 2ad to find stopping distance where

vf = final velocity =0

v0 = initial velocity = 14.72m/s

a = acceleration

d = distance traveled = stopping distance

we can find the acceleration knowing that F = ma, and in the case of friction, f = u mg, so that

m a = u m g or a = u g

in this case, a =- 0.1 x 9.8m/s/s = -0.98m/s/s the acceleration will be negative since it opposes motion

therefore,

0=(14.72m/s)^2 +2(-0.98m/s/s) d => d = 110.6m

if the coefficient of friction were 6 times greater, the accel would be 6 times greater and the stopping distance would be 1/6 as much, so it would be 18.4m

thats cheating