3. The square block with mass m and thickness d is statically placed on a smooth horizontal plane. As shown in the figure, a bullet with mass m penetrates the block horizontally at the initial velocity V0, and the resistance of the bullet is f and remains unchanged. In the process of the bullet penetrating the block, the displacement of the block is L. what are the velocities of the bullet and the block after the bullet passes through the block?

3. The square block with mass m and thickness d is statically placed on a smooth horizontal plane. As shown in the figure, a bullet with mass m penetrates the block horizontally at the initial velocity V0, and the resistance of the bullet is f and remains unchanged. In the process of the bullet penetrating the block, the displacement of the block is L. what are the velocities of the bullet and the block after the bullet passes through the block?

Due to the momentum conservation in the collision process: MV0 = MV1 + MV2 due to the functional principle: 0.5mv0 ^ 2-0.5mv1 ^ 2-0.5mv2 ^ 2 = fdv1 is the velocity after M collision, V2 is the velocity after M collision. Note that because the wood block and bullet receive the action of F, and the direction is opposite, the internal force work is FD, and the solution is V1 = (m ^ 2v0 + (2m ^ 4v0 ^ 2-2m ^ 3M +)