Question

A truck traveling at 75 mi/h has a braking efficiency of 70%. The coefficient of road adhesion is 0.80. Ignoring aerodynamic resistance, determine the theoretical stopping distance on a level grade.

Answer 1

Answer:100.36 m

Explanation:

Given

speed of truck $u=75 mi/hr\approx 33.528\ m/s$

Braking efficiency of 70 %

i.e. braking declaration will be 70 % of frictional force

$\mu =0.8$

$a_{max}=\mu g=0.8\times 10=8 m/s^2$

effective acceleration $a_{eff}=0.7\times 8=5.6\ m/s^2$

using equation of motion

$v^2-u^2=2 a s$

where v=final velocity

u=initial velocity

a=acceleration or declaration

s=displacement

here v will be zero

$-(33.528)^2=2(-5.6)(s)$

$s=\frac{33.528^2}{2\times 5.6}$

$s=100.36 m$