Question

A motor car of mass 1200 Kg is moving along a straight line with uniform velocity of 90 Km/h. Its velocity is slowed down to 18 Km/h in 4sec. by an unbalanced external force. Calculate the acceleration and change in momentum. Also calculate the magnitude of external force acting on it.

Answer 1

given:
mass(m)=1200kg
initial velocity (u)=90km/hr
=90*5/18=25m/s
final velocity (v)=18km/hr
=5m/s
time (t)=4s

v=u+at
5=25+4a
-20=4a
a=-5m/s²

change in momentum=m(v-u)
=1200(5-25)
=1200*-20
=-24000m/s

force =ma
=1200*-5=-6000N

this negative sign represents direction.

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!!!!