Question

A bullet of mass 4.7 g is fired horizontally into a 2.4 kg wooden block at rest on a horizontal surface. The coefficient of kinetic friction between block and surface is 0.28. The bullet stops in the block, which slides straight ahead for 2.2 m (without rotation). (a) What is the speed of the block immediately after the bullet stops relative to it? (b) At what speed is the bullet fired?

Answer 1

work done by block/bullet= totalmass*g*mu*distance

from that, compute the initial velocity of the block/bullet system (workdone=1/2 mv^2)

Now, knowing that velocity, use the conservation of momentum to find the initial velocity of the bullet

massbullet*vbullet= totalmass*Vyoufound