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Question
A bullet of mass 20 g enters into a fixed wooden block with a speed of 40 m s−1 and stops in it. Find the change in internal energy during the process.
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Solution
Given:-
Mass of bullet, m = 20g = 0.02 kg
Initial velocity of the bullet, u = 40 m/s
Final velocity of the bullet = 0 m/s
`"Initial kinetic energy of the bullet"=1/2m u^2=1/2xx0.02xx40xx40=16J`
Final kinetic energy of the bullet = 0
Change in energy of the bullet = 16 J
It is given that the bullet enters the block and stops inside it. The total change in its kinetic energy is responsible for the change in the internal energy of the block.
∴ Change in internal energy of the block = Change in energy of the bullet = 16 J
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