AP CollegeBoard Scoring Guide Unit 4.3 Conservation of Momentum and Collisions 19. 4.0 m/s Before Jump After Jump As shown in the figure above, a child of mass 20 kg who is running at a speed of 4.0 m/s jumps onto a stationary sled of mass 5.0 kg on a frozen lake. The speed at which the child and sled begin to slide across the ice is most nearly (A) 0.20 m/s (B) 0.80 m/s (C) 1.2 m/s (D) 3.2 m/s (E) 16 m/s 20. Object A of mass M is moving east at speed v. It collides with object B of mass 2M that was initially at rest. The motion of the objects before and after the collision is along the same line. After the collision, object A is moving west at a speed of w/3. What is the speed of object B immediately after the collision? (A) w/3 (B) v/2 (C) 2v/3 (D) V (E) 2v15. X 6 m/s x 10 m/s 530 Figure I Figure II Two balls are on a frictionless horizontal tabletop. Ball X initially moves at 10 meters per second, as shown in Figure I above. It then collides elastically with identical ball Y, which is initially at rest. After the collision, ball X moves at 6 meters per second along a path at 53 to its original direction, as shown in Figure II above. Which of the following diagrams best represents the motion of ball Y after the collision? AP Physics C. Mechanics Page 9 of 22 Scoring Guide Unit 4.3 Conservation of Momentum and Collisions 1=0 (A) (B) 10 m/'s (C) 04 m/s (D)(E) 16. An object having an initial momentum that may be represented by the veclor above strikes an object that is initially at rest. Which of the following sets of vectors may represent the momenta of the two objects aer the collision? (A) # (B) _' (C) \"' _' (D) ' (E) V' AP Physics C: Mechanics Page 1 1 of 22 l-rl. In an experiment, block 1 is Jgiven an initial speed on toward block 2. which is initially at rest. The blocks are on a track tltat has a motion detector set up. as shown above. When tlte two blocks collide, there is a completely inelastic collision and the blocks move together with speed Bf. The blocks were both placed on a balance, and it is determined that they have the same mass. The experiment is repeated for four different initial speeds. and the data are shown in the chart below. It appears that the resulting data are not accurate. Which measurement most likely produced errors in the data seen in the chart below? (A) The mass of block 1 is accurate, but the mass of block 2 is actually less massive than recorded. (B) Both mass values are accurate. but on is actually larger than recorded. (C) The motion sensor was positioned too close to block 1. {D} The nal velocity recorded was taken too long after the collision V'i (E} The data recorded is accurate within acceptable experimental error. "II-II 'I'I-P \\(uuncl 'lluu "I JJ'IUIIIFIIIIIIII nuu \ -IIIIIHII'II, 1'1. A student drops a bag of mass t. onto a cart of mass M that is sliding with speed on along a horizontal track with negligible friction. Immediately after the bag lands in the cart, the cart-bag system moves with speed 1);. Which of the following statements correctly relates the two speeds and gives a correct reason for this relationship? (A) v; on, because the kinetic energy of the bag decreases. (D) U; > no, because the linear momentum of the bag is added to the linear momentum of the cart (E) v; = I)\(1:) or: 11. Block Block B A Vo r m Ln an experiment to study collisions, block A with of mass m] is moving speed so when it collides with block B of mass mg which is initially at rest. After the collision. the blocks stick together and move on" With speed of. For a series ol'eollistons, block A is given different initial velocities. The graph ofvf as a function of'un is shown. How would doubling mass ml change the graph? Vr V0 Page 6 of 22 AP Physics C: Mechanics m scan-aim Unit 4.3 Conservation of Momentum and Collisions (A) The slope of the graph line would be less. (B) The slope of the graph line would be greater. '/ (C) The graph line would no longer be linear. (D) There would be no effect on the graph. [E] The change cannot be determined without knowing the ratio of %_ 12. An object moving on a horizontal, frictionless surface makes a glancing collision with another object initially at rest on the surface. In this case which ol'the following is true about momentum and kinetic energy? IA) Momentum is always conserved. and kinetic energy may be conserved. '/ (B) Kinetic energy is always conserved. and momentum may be conserved. (C) Momentum is always conserved. and kinetic energy is never conserved. (D) Both momentum and kinetic energy are always conserved. (E) Neither momentum nor kinetic energy is conserved. 13. A balloon of mass M is floating motionless in the air. A person ofmass less than M is on a rope ladder hanging from the balloon. The person begins to climb the ladder at a uniform speed v relative to the ground. How does the balloon move rclalive to the ground'.' (A) Up with speed it (B) Up with a speed less than v (C) Down with speed v I (D) Down with a speed less than v I (E) The balloon does not move