Energy is absorbed by the block. How much? depends on angle of swing.
Energy absorbed= Mgh=Mg(L- Lcos α) and that is equal to energy in the bullet initially minus the enrgy it leaves with.
1/2 m vb2^2=1/2 m vb1^2-MgL(1-cos α)
and from that, you can calculate vb2
A block of mass M is hanging from a string of length L at velocity vb1. A bullet (mass b) is shot at the block. It passes through the block with a velocity of vb2. As a result, the block swings upwards and comes to a stop at an angle of α above the starting position.
What is the initial velocity of the block in terms of L, α, and M? I don't understand how L and α are in the end answer but that's what is specified in this problem. I used momentum and energy formulas.
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