Question

a motor car of mass 1200 kg is moving along a straight line with a uniform velocity of 90 km / h its velocity is slowed down to 18 km/ h in 4 sec by an unbalanced force calculate the accelaration and change in momentum also calculate the magnitude of the force required​

Answer 1

m=1200kg

u=90km/h

=>90×5/18=25m/s

v=18km/h

=>18×5/18=5m/s

t=4s

Thus,acceleration of the body is------

a=(v-u)/t

a=(5-25)/4

a=-20/4

a= -5m/s²

Thus,change in momentum of the body is------

mv-mu

1200×5-1200×25

1200(5-25)

1200×(-20)

-24000 kg m/s

Thus,the magnitude of force required is------

F=ma

F=1200×(-5)

F= -6000N,or 6000N in the opposite direction.

Answer 2

Answer:

initial velocity = 90km/h = 90 ×5/18 m/s = 25m/s

final velocity = 18 km/h = 18× 5/18 m/s = 5 m/s

acceleration = (final velocity -initial velocity )/ time taken

=( 25 - 5)/4 = 5 m/s²

now,

change in momentum = m( final velocity - initial velocity )

=1200 ×( 25 - 5) = 24000 Kgm/s

force = change in momentum / time

= 24000/4 = 6000 N