Question

Find the average force needed to accelerate a car weighing 500 kg from rest to 72 km/h in a distance of 25 m.

Answer 1

Given,

Mass $m=500kg$,

Initial velocity u = 0,

Final velocity $v=72km/h=20m/sec$,

Dispalcement = $s=50m$.

From third equation of motion we have,

$a=\frac{(v^2-u^2)}{2s}$

$=\frac{400}{50}=8m/se{c}^2$

Force needed to accelerate the car,

$F=ma=500\times 8=4000N$.