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In some demonstration, a police officer ...

In some demonstration, a police officer fires a bullet of mass 50.0g with speed `200ms^(-1)` on soft plywood of thickness 2.00 cm. The bullet emerges with only 10% of its initial kinetic energy. What is the emergent speed of the bullet?

Text Solution

Verified by Experts

The initial kinetic energy of the bullet is `mv^(2)"/"2= 1000 J`. It has final kinetic energy of `0.1xx1000= 100 J`. If `v_(f)` is the emergent speed of the bullet,
`(1)/(2) mv_(f)^(2)= 100 J`
`v_(f)= sqrt((2xx100 J)/(0.05 kg))`
`= 63.2 ms^(-1)`.
The speed is reduced by approximately 68% (not 90%).
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