Question

A 2000 kg car starts from rest and coasts down from te top of 5m long driveway that is sloped at an angle of 20 degrees with the horizontal. If a constant 4000N frictional force resists the car's motion, find the speed of the car at the bottom of the driveway?

Answer 1

Answer:3.67 m/s

Explanation:

Given

mass of car $m=2000 kg$

Initial velocity $u=0$

Length of track $L=5 m$

inclination of driveway $\theta =20^{\circ}$

Friction Force $F=4000 N$

Sin component of weight accelerate the car while friction tries to oppose the car i.e.

$mg\sin \theta -F=ma_{net}$

$a_{net}=g\sin \theta -\frac{F}{m}$

$a_{net}=9.8\sin 20-2=1.35 m/s^2$

Using $v^2-u^2=2 as$

$v=final\ velocity$

$v=\sqrt{2\times 1.35\times 5}$

$v=\sqrt{13.517}=3.67 m/s$