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NTA Abhyas 2020

Exam: NTA Abhyas
Year: 2020
Subject: Physics
Chapter: Center of Mass, Momentum and Collision

NTA Abhyas 2020 · Physics · Center of Mass, Momentum and Collision

A 12 kg bomb at rest explodes into two pieces of 4 kg and 8 kg. If...

A

12

kg bomb at rest explodes into two pieces of

4

kg and

8

kg. If the momentum of

4

kg piece is

20Ns

, the kinetic energy of the

8

kg piece is

Options

A $25J$
B $20J$
C $50J$
D $40J$

Correct answer

A. $25J$

Step-by-step solution

The explosion is due to internal forces so the momentum of the system is conserved.

Applying conservation of momentum,

0 = {m}_{1}v + {m}_{2}v′0 = 20 + 8v′

v′ = \dfrac{- 20}{8} = \dfrac{- 5}{2}ms^{- 1}

After the explosion,

Then,

KE = \dfrac{1}{2}mv{′}^{2}

= \dfrac{1}{2} \times 8 \times \left(\dfrac{5}{2}\right)^{2} = \dfrac{1}{2} \times 8 \times \dfrac{25}{4} = 25J

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