A bullet fired at a wooden block of thickness 0.15m manages to penetrate the block. If the mass of the bullet is 0.025kg and the average resisting force of ...

The work done by the resisting force of the wooden block is equal to the kinetic energy of the bullet just before it hits the wooden block. Therefore, we can equate the work done by the resisting force to the kinetic energy of the bullet: Work done = Force x distance = average resisting force x thickness of the block Kinetic energy of the bullet = (1/2) x mass x velocity^2 Since the bullet manages to penetrate the wooden block, we can assume that all its kinetic energy is used up in overcoming the resisting force of the wooden block. Therefore, we can equate the two expressions: (1/2) x mass x velocity^2 = average resisting force x thickness of the block Substituting the given values, we get: (1/2) x 0.025 x velocity^2 = 7.5 x 10^3 x 0.15 Simplifying this equation, we get: velocity^2 = (2 x 7.5 x 10^3 x 0.15) / 0.025 velocity^2 = 90,000 Taking the square root of both sides, we get: velocity = 300 m/s Therefore, the speed of the bullet just before it hits the wooden block is 300m/s. So the answer is from the given options.