12.1 Object A is moving when it has a head-on collision with stationary object B. No external forces act on the objects. Which of the following situations are possible after the collision? Identify all that are possible. a. A and B move in the same direction b. A and B move in opposite directions C. A moves and B is stationary d. A is stationary and B moves e. A and B are both stationary 12.2 Suppose an empty railroad car is rolling without friction V v snow V on a level track. Snow begins to fall vertically, filling the car. As time passes the car's speed... CO a. increases. b. decreases. c. remains at the same 12.3 Drop a stone from the top of a high building. It speeds up. So is momentum conserved? Yes No Maybe OK. This is a trick question. Like Energy, Momentum is ALWAYS conserved in physics Identify the system wherein the net momentum is zero as the stone falls. In other words, what is the system for which momentum is conserved? 12.4 A rifle fires a bullet of mass 0.0300 kg which leaves the barrel with a positive velocity of 400 m/s. The mass of the rifle is 3.00 kg. At what velocity does the rifle recoil? Show your work! (Equation, substitution of variables, answer).13. (AP Exam from 2002-a few years before you were Born!) 3.0 m/s A 2.0 kg frictionless cart is moving at a constant speed of 3.0 m/s to the right on a horizontal surface as shown to the right. Cart 2 2.0 kg is initially at rest. (a) Based on the impulse graph to the right, calculate the velocity Time t (ms) of the 2.0 kg cart after the collision. 0.0 0.5 1.0 0 Force F (kN) - 6 (b) After the collision, initially stationary cart 2 travels with a -12 velocity of 2.0 m/s. Calculate the mass m of the second cart. (c) What percent of the initial kinetic energy is lost in the collision? After the collision, the second cart eventually 2.0- experiences a ramp, which it transverses with no frictional losses. The graph Speed u (m/s) below shows the speed v of the second cart as a function of time t for the next 5.0 s, where t = 0 is1.0 now the instant at which the carts separate. (d) Identify whether the ramp goes up or down (circle): UP DOWN Time ? (s) (e) calculate the maximum elevation (above the initial height) reached by the second cart on the ramp after the collision