Question

A motorcar of mass 1200Kg is moving along a straight line with a uniform velocity of 90 km/hr. Its velocity is slowed down to 18 km/hr in 4 sec by an unbalanced external force. Calculate the acceleration and change in momentum also calculate the mangitude of the force required.

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.