Question

A truck starts from rest and rolls down a hill with a constant acceleration. It travels a distance of 400 m in 20 s. Find its acceleration. Find the force acting on it if its mass is 7 tonnes (Hint: 1 tonne = 1000 kg.)

Answer 1

The truck starts from rest, so initial velocity u = 0, Distances= 400 m, t= 20 s, m= 7 tons = 7 × 1000 = 7000 kg,
From 2nd equation of motion,
$s=ut+\frac{1}{2}at^2$
= 400 = 0 × 20 + $\frac{1}{2}$ × a × (20)2
= 400
= 200a
⇒ a = 2ms-2
From Newton's 2nd law of motion, force acting on the truck
F = ma = 7000 × 2 = 14000N = 1.4 × 104 N