When the wood block with mass m = 3M is fixed on a smooth horizontal plane, a bullet with mass m is fired into the wood block along the horizontal direction at the velocity V0, and the velocity of the bullet passing through the wood block is V03; now when the same wood block is placed on a smooth horizontal plane, and the same bullet is still fired into the wood block along the horizontal direction at the velocity V0, the bullet () A. It can't shoot through the wood block, the bullet and the wood block move at the same speed. B. It can shoot through the wood block. C. It can just shoot through the wood block, and the speed of the bullet is 0d. It can just shoot through the wood block, and the speed of the bullet is greater than V03

When the wood block with mass m = 3M is fixed on a smooth horizontal plane, a bullet with mass m is fired into the wood block along the horizontal direction at the velocity V0, and the velocity of the bullet passing through the wood block is V03; now when the same wood block is placed on a smooth horizontal plane, and the same bullet is still fired into the wood block along the horizontal direction at the velocity V0, the bullet () A. It can't shoot through the wood block, the bullet and the wood block move at the same speed. B. It can shoot through the wood block. C. It can just shoot through the wood block, and the speed of the bullet is 0d. It can just shoot through the wood block, and the speed of the bullet is greater than V03

When the wood block is fixed, according to the kinetic energy theorem, - FD = 12m (V03) 2 − 12mv02, the solution is FD = 49mv02. When the wood block is not fixed, assuming that the bullet can not shoot out of the wood block, according to the law of conservation of momentum, MV0 = (M + m) V, the solution is v = V04. According to the law of conservation of energy, f △ x = 12mv02 − 12 (M + m) V2 = 38mv02 ＜ FD, it can be known that △ x ＜ D, so the assumption is true, the bullet can not shoot out of the wood block, and finally the bullet is fired A is right, B, C and D are wrong, so choose a