Question

A force of $1500N$ acts on a car at rest for $2s$ to make it move with a uniform velocity of $30m/s$. Calculate:
(i) Change in momentum of the car
(ii) Mass of the car

Answer 1

Given that,

Force $F=1500N$

Time $t=2s$

Velocity $v=30m/s$

Now, change in momentum of the car is

$F_{net}=\frac{\Delta p}{\Delta t}$

$\Delta p=F_{net}\times \Delta t$

$\Delta p=1500\times 2$

$\Delta p=3000kgm/s$

Now, the mass of car is

$F=m\frac{\Delta v}{\Delta t}$

$\frac{F\times \Delta t}{\Delta v}=m$

$m=\frac{1500\times 2}{30}$

$m=100kg$

Hence, the mass of a car is $100kg$ and change in momentum of the car is $3000kgm/s$