A railway truck of mass 4 x 10*kg moving at a velocity of 3 ms collides with another truck of mass 2 x 10* kg which is at rest. The couplings join and the trucks move off together. What fraction of the first truck's initial kinetic energy remains as kinetic energy of the two trucks after the collision? Is energy conserved in a collision such as this? Explain your answer briefly. [L)

A 4.0 kg box slides on a horizontal frictionless table and collides with a 1.6 kg box initially at rest on the edge of the table, at height h = 1.0 m. The speed of the 4.0 kg box is 3.6 m/s just before the collision. If the two boxes stick together because of packing tape on their sides, what is their kinetic energy just before they strike the floor? (Your result must be in Joules and include 1 digit after the decimal point. Maximum of 2% of error is accepted in your answer. Take g=9.8 m /s 2.)

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A 0.017-kg bullet is fired into a stationary block of wood of mass of 4.7 kg. The relative speed of the bullet with respect to the wood is zero after collision (The bullet becomes embedded on the block of wood). If the speed of the bullet before collision is 472 m/s, what is the kinetic energy of the bullet-plus-wood combination right after the collision? Assume no change in the potential energy of the system before and after the collision. Express your answer in two decimal places, in Joules.