1. A 5000-kg train moving at 5.0 m/'s [S] collides with another train of equal mass at rest and the two trains become coupled. Calculate the speed of the coupled trains after collision. 2. A billiard ball of mass 0.20 kg moving at 3.0 m/'s [right] strikes an identical ball moving in the opposite direction at 1.0 m/s. If the velocity of the second ball after collision is 2.0 m/'s [right], what is the velocity of the first ball after collision? 3. A train loaded with steel, moving at 90 km/h, collides head on with a stationary train of mass 6000 kg. If the trains couple after collision and move forward with a velocity of 80 km/h, find the mass of the train loaded with steel. 4. Three coupled freight cars, each of mass m, are traveling with a constant speed v on a straight and level track. They collide with two coupled stationary cars, each of mass 2m. If all five cars are coupled together after collision, what is their common speed? 5. A police investigator doing some ballistics testing in his laboratory fires a 30-g bullet with a velocity of 360 m/s into a lead paperweight placed against a concrete wall. Because of a constant resistance force, the bullet penetrates 5.0 cm into the paperweight before coming to a stop. Calculate a) the initial momentum of the bullet before the collision. b) the acceleration of the bullet in the paperweight. c) the average force exerted on the bullet. d) the time required to stop the bullet in the paperweight. 6. A rifle bullet of mass 5.0 x 10" kg strikes and embeds itself in a block of mass 4.95 x 10"kg which rest on a horizontal frictionless surface. The block is attached to a coil spring and the impact compress the spring 10.0 cm as shown in the diagram on the right. 10.0 em The spring constant is 2.0 x 10"N/m a) Find the maximum elastic potential energy of the spring. b) Find the speed of the block and bullet just after the impact. c) What was the initial velocity of the bullet just before it strikes the block? 7. A 5.0 x 10-"kg bullet strikes and becomes Fast embedded in a wooden block of mass 4.5 x 10" kg which is at rest on a horizontal frictionless surface and is attached to a spring bumper. The block and bullet compress the spring bumper a distance of 20.0 centimeters as shown on the right. The spring constant is 2.0 x 10'N/m Before interaction After interaction a) Find the maximum elastic potential energy of the spring. b) Find the speed of the block and bullet just after the impact. c) What was the initial velocity of the bullet just before it strikes the block