A 0.0315-kg bullet is fired horizontally into a 4.83-kg wooden block attached to
ID: 1366501 • Letter: A
Question
A 0.0315-kg bullet is fired horizontally into a 4.83-kg wooden block attached to one end of a massless, horizontal spring (k = 806 N/m). The other end of the spring is fixed in place, and the spring is unstrained initially. The block rests on a horizontal, frictionless surface. The bullet strikes the block perpendicularly and quickly comes to a halt within it. As a result of this completely inelastic collision, the spring is compressed along its axis and causes the block/bullet to oscillate with an amplitude of 0.171 m. What is the speed of the bullet?
Explanation / Answer
using energy conservation,
intial kinetic energy = (4.83 +0.0315)v^2 /2
initial spring PE = 0
final KE = 0
final spring PE = kx^2 /2 = 806 x 0.171^2 /2
(4.83 +0.0315)v^2 /2 + 0 = 0 + 806 x 0.171^2 /2
v = 2.20 m/s
now using momentum conservation on block - bullet,
initial momentum = final momentum
0.0315u + 4.83 x 0 = (4.83 +0.0315) x 2.20
u = 339.81 m/s
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