Question

a 1.5 Mg car moving along a concrete road has its brakes locked and skids to a smooth stop. calculate the force of friction (a) on a dry road and (b) on a wet road. (coefficient of kinetic friction for rubber: wet: 0.97; dry: 1.02)

Answer 1

Coefficient of friction \(\mu\) is
\[\mu = \frac{\text{force of friction}}{\text{normal force}}\]
For a horizontal surface like this, normal force is the same as weight.
So force of friction \(F_f\) is
\[F_f = \mu m g\]
where \(m\) is mass (1500 kg) and \(g\) is acceleration due to gravity (9.8 ms\(^{-1}\))