Question

A truck of mass 7 tonnes 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 and the force acting on it.

Answer 1

Given data

1. Mass of the truck is $m=7tonnes=7000kg$. ($1tonne=1000kg$)
2. Initial velocity is $u=0m/s$ (Truck starts from rest)
3. Distance travelled is $s=400m$
4. Time taken is $t=20s$

Calculation of acceleration

1. Acceleration can be calculated by using the relation, $s=ut+\frac{1}{2}a{t}^2$, where $a$ is the acceleration of the body.
2. Putting all the given values in the equation.
3. $400=0\times 20+\frac{1}{2}\times a\times {\left(20\right)}^2.$
4. $400=\frac{400a}{2}.$
5. $a=2m/s^2.$

Calculation of Force

1. According to the second law of motion, $F=ma$.
2. $F=7000\times 2=14000N.$

Hence, the acceleration of the truck is 2m/s² and the force is $14000N$.