Question

A boy was playing with the ball on the roof of his building. He dropped the ball from the building of height 5m. The ball of 2g moves at 100 m/s . Find the momentum of the ball

Answer 1

let the downward velocity be V

1

and upward velocity be V

2

now V

1

=

2gh

1

=

2×9.8×2

=

4×9.8

=2

9.8

momentum before collision = mV

1

= 100×10

−3

×2

9.8

=0.626

s

kgm

after collision V

2

=

2gh

2

=

2×9.8×1.5

=

3×9.8

momentum after collision = −mV

2

=−100×10

−3

3×9.8

= −0.542

s

kgm

direction is reverse therefore negative sign assigned

△P=P

f

−P

i

= -0.542-0.626 = -1.168

F=

△t

△P

=1.168×10

8

N