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## Homework Statement

A bullet leaves the muzzle of a rifle at an unknown velocity and strikes a wooden block that is suspended by a piece of string.

If the block swings backwards to make an angle of 40 degrees, at what velocity must have the bullet been travelling when it struck the block?

mass of the bullet and the wood are, respectively, m=0.05 kg and M=2 kg, and the length of the string is L=1 m. Theta = 40 degrees

[PLAIN]http://img810.imageshack.us/img810/5295/bullet.jpg [Broken]

## Homework Equations

## The Attempt at a Solution

The block is given kinetic energy equal to the kinetic energy the bullet had.

Since the block experiences no friction, all of this kinetic energy is used up by moving against gravity.

s and f can be determined and so the energy can be calculated

with f x s = energy

Then use (1/2)mv^2 = energy to calculate the speed of the bullet

The problem is that I'm unsure how to calculate s. How can this be done? (s = vertical displacement of the block)

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