Forensic scientists can measure the muzzle velocity of a gun by firing a bullet

Question

Forensic scientists can measure the muzzle velocity of a gun by firing a bullet horizontally into a large hanging block that absorbs the bullet and swings upward. The measured maximum angle of swing can be used to calculate the speed of the bullet. In one such test, a rifle fired a 4.20g bullet into a 2.50kg block hanging by a thin wire 75.0CM long, causing the block to swing upward to a maximum angle of 32.7 DEGREES from the vertical

What was the original speed of this bullet?
v =________________m/s}

Explanation / Answer

conserving momentum,

0.0042*v = 2.5042*v'

So, v' = 0.0042*v/2.5042

so, 0.5*2.5042*(0.0042*v/2.5042)^2 = 2.5042*9.8*0.75*(1-cos(32.7 degrees))

So, v = 910.1 m/s <---------------answer

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