Question

Traveling at a speed of 18.5 m/s, the driver of an automobile suddenly locks the wheels by slamming on the brakes. The coefficient of kinetic friction between the tires and the road is 0.630. What is the speed of the automobile after 1.25 s have elapsed? Ignore the effects of air resistance.

Answer 1

Answer:

10.774625 m

Explanation:

t = Time taken

u = Initial velocity

v = Final velocity

s = Displacement

a = Acceleration

g = Acceleration due to gravity = 9.81 m/s²

$\mu$ = Coefficient of kinetic friction = 0.63

m = Mass

f = Frictional force

$a=-\frac{f}{m}\\\Rightarrow a=-\frac{\mu mg}{m}\\\Rightarrow a=-\mu g$

Equation of motion

$v=u+at\\\Rightarrow v=u-\mu gt\\\Rightarrow v=18.5-9.81\times 0.630\times 1.25\\\Rightarrow v=10.774625\ m/s$

The speed of the automobile after the time has elapsed is 10.774625 m