Question

A motor car of mass 1200 kg is moving along a straight line but with uniform velocity of 90km/hr.its velocity is slowed doen down to 18km/hr in 4 seconds by an external force.calculate the acceleration change in momentum and the magnitude of 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.

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