A 12.0 g rubber bullet travels at a velocity of 150 m/s, hits a stationary 8.5 kg concrete block resting on a frictionless surface, and ricochets in the opposite direction with a velocity of -100. m/s. How fast will the concrete block be moving?

Use the to answer this question.

Calculate the total momentum before the collision. momentum of bullet = mass x velocity = 0.012 x 150 = 1.8 N.s (note the mass of the bullet is in grams) momentum of block = mass x velocity = 8.5 x 0 = 0 N.s

total momentum = 1.8 + 0 = 1,8 N.s

Then find the total momentum after the collision momentum of bullet = 0.012 x (-100) = -1.2 N.s (note sign tells us it is in the opposite direction) momentum of block = 8.5 x v

Total momentum = -1.2 + 8.5v

But the total momentum is always conserved

so 1.8 = -1.2 + 8.5v 3 = 8.5v v = 3/8.5 = 0.35 m/s