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A 10 g bullet is fired horizontally into a 100 g wooden block that is initially

ID: 1459913 • Letter: A

Question

A 10 g bullet is fired horizontally into a 100 g wooden block that is initially at rest on a frictionless horizontal surface and connected to a spring having spring constant 143 N/m. The bullet becomes embedded in the block. If the bullet- block system compresses the spring by a maximum of 90 cm , what was the speed of bullet at impact with the block? A 10 g bullet is fired horizontally into a 100 g wooden block that is initially at rest on a frictionless horizontal surface and connected to a spring having spring constant 143 N/m. The bullet becomes embedded in the block. If the bullet- block system compresses the spring by a maximum of 90 cm , what was the speed of bullet at impact with the block?

Explanation / Answer

by conservation of energy

initial energy = final energy

0.5 * mv^2 = 0.5 * kx^2

0.5 * 0.1 * v^2 = 0.5 * 143 * 0.9^2

v = 34.034 m/s

by conservation of momentum

initial momentum = final momentum

10 * 10^-3 * vb = (10 + 100) * 10^-3 * 34.034

vb = 374.374 m/s

speed of bullet = 374.374 m/s