Question

A motor car of mass 1200 kg is moving along a straight path with a uniform velocity of 90 kmph. It's velocity slows down to 18 kmph in 4 sec by an unbalanced force. Calculate the acceleration and change in momentum also calculate the magnitude of force required.

Answer 1

90kmph=25mps
18kmph=5 m per sec
v=u+at
5=25-a*4
a=-5
rate of change in momentum=force req
m(v-u)=1200(25-5)=24000
rate = 24000/4= 6000
or f=ma →5*1200=6000

Answer 2

HELLO FRIEND HERE IS YOUR ANSWER,,,,,,,,

Refer and consult the following attachments for a detailed explanation and step by step solution along with time by time elaborations to reach the final conclusion in our answers....

[Check attachments for explanation]

$\boxed{\bf{Acceleration \: of \: this \: vehicle = a = - 5 \: m/s^2}}$

$\boxed{\bf{Change \: in \: momentum \: of \: this \: vehicle = M_{(v - u)} = - 24000 \: Kg \: m/s}}$

Magnitude of the force required to slow down the vehicle by an unbalanced external force;

$\boxed{\bf{F = - 6000 \: N}}$

HOPE THIS HELPS YOU AND CLEARS THE DOUBTS!!!!