Bullet & Wooden Block?

Question

A bullet with a mass of 7.00 g, traveling horizontally with a speed of 430 m/s, is fired into a wooden block with mass of 0.850 kg, initially at rest on a level surface. The bullet passes through the block and emerges with its speed reduced to 200 m/s. The block slides a distance of 46.0 cm along the surface from its initial position.

Part A: What is the coefficient of kinetic friction between block and surface?

Part B: What is the decrease in kinetic energy of the bullet?

Part C: What is the kinetic energy of the block at the instant after the bullet passes through it?

Answer 1

Start with B. Calculate the KE before and after using
KE = (1/2)*m*v^2
Subtract.

C. Momentum is always conserved.
m1*u1 + m2*u2 = m1*v1 + m2*v2
Find the block's speed, v2.
Calculate the block's KE

A. The block's KE after the bullet passes through was all dissipated by friction.
KE = work by friction
KE = Ff*d
KE = mu*m*g*d