Question

how much work is needed to be done on a ball of mass 20g to give it a momentum of 10kgm/s?

Answer 1

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Answer 2

Given :

initial velocity ( u ) = 0 m/s

final velocity ( v ) = ?

mass ( m ) = 20g

                 = 20 / 1000 kg

                  = 0.02 kg

Momentum ( p ) = 10 kg m/s

Formula :

Momentum = mass × velocity

Calculate the final velocity :

10 kg m/s  = 0.02 kg × v

= > v = 10 kg m/s / ( 0.02 kg )

= > v = 500 m/s

Formula :

Work = change in kinetic energy

= 1/2 m v² - 1/2 m u²

1/2 m u² = 0 because u = 0

Hence work = 1/2 m v²

Find the work:

W = 1/2 m v²

= > W = 1/2 × 0.02 × (500)²

= > W = 1/2 × 0.02 × 500 × 500

= > W = 1/2 × 2 × 500

= > W = 1 × 500

= > W = 500 J

ANSWER :  The work done is 500 J