1.

A bullet moving with a speed of 150 ms^(-1) strikes a wooden plank. After passing through the plank its speed becomes 125 ms^(-1). Another bullet of the same mass and size strikes the plank with a speed of 90 ms^(-1). Its speed after passing through the plank would be:

Answer»

`50 ms^(-1)`
`35 ms^(-1)`
`25 ms^(-1)`
`70 ms^(-1)`

Solution :Work done=change in K.E.
`:. Fxxx=1/2m[(150)^(2)-(125)^(2)]`
Also `Fxxx=1/2m[(90)^(2)-V^(2)]`
`:. (150)^(2)-(125)^(2)=(90)^(2)-v^(2)`
Solving it,we get v=35 m/s.


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