Question

Agent Arlene devised the following method of measuring the muzzle velocity of a rifle. She fires a bullet into a 4.200-kg wooden block resting on a smooth surface, and attached to a spring of spring constant k = 145.0 N/m . The bullet, whose mass is 7.750 g , remains embedded in the wooden block. She measures the maximum distance that the block compresses the spring to be 9.460 cm.

Part A

What is the speed v of the bullet? Express your answer using four significant figures.

Answer 1

Using law of conservation of energy,

(145 x 0.0946^2) = (4.2 + 0.00775) v^2

Velocity, v = 0.555 m/s

Using law of conservation of momentum,

0.00775 v = (4.2 + 0.00775) x 0.555

V = 301.33 m/s

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