Forensic science. Forensic scientists can measure the muzzle velocity of a gun b

Question

Forensic science.
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. (See the figure below.) 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 32.2degrees from the vertical. (Figure 1)

FIGUR 1: http://session.masteringphysics.com/problemAsset/1342813/2/yg.8.48.jpg

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

Explanation / Answer

?h = 0,75*(1-cos32.2°) = 0.115 m V = v2gh = v19,6*0.115 = 1,50 m/sec applying momentum conservation principle : I = M*V = 2.504*1.50 = 3,76 kgm/sec 3.76 = 0,0042*Vb Vb = 3.76/0.0042 = 895 m/sec

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