A0.00545-kg bullet is fired straight up at a falling wooden block that has a mass of 3.08 kg. the bullet has a speed of 720 m/s when it strikes the block. the block originally was dropped from rest from the top of a building and had been falling for a time t when the collision with the bullet occurs. as a result of the collision, the block (with the bullet in it) reverses direction, rises, and comes to a momentary halt at the top of the building. find the time t.