A 8.0 g bullet is fired into a 9.00 kg wood cube that is initially at rest. The bullet lodges in the cube, and the combined system moves forward with a velocity of 40 cm/s. What was the initial veloci

Here is the solution:

Given:
Mass of bullet, $m_b = 8.0 \, \text{g} = 0.008 \, \text{kg}$
Mass of wood cube, $m_w = 9.00 \, \text{kg}$
Initial velocity of wood cube, $u_w = 0 \, \text{m/s}$ (at rest)
Final velocity of the combined bullet and wood cube, $V = 40 \, \text{cm/s} = 0.40 \, \text{m/s}$
Initial velocity of bullet, $u_b = ?$