Body 1 and body 2 are in a completely inelastic one-dimensional collision. What

Question

Body 1 and body 2 are in a completely inelastic one-dimensional collision. What is their final momentum if their initial momenta are -12 kg.m/s and -3.5 kg.m/s? 15.5 kg m/s -15.5 kg m/s 9.5 kg.m/s 8.5 kg.m/s -8.5 kg-m/s Suppose a little calculator and a big physics text are sliding toward you on a frictionless air table. Both have the same and you exert the same force to stop each. How do the time intervals to stop them compare? It takes less time to stop the little calculator. Both take the same time. It takes more time to stop the little calculator. Impossible to tell without knowing actual masses of the calculator and the book. A steel ball strikes a wall with an initial momentum p_i at an angle theta with the surface. It bounces off with momentum p_f at the same speed and angle. The direction of the impulse vector J = Delta p is along the positive x-axis along the negative x-axis along the positive y-axis in the same direction as p_i in the same direction as p_f Consider these situations: a ball moving at velocity v is brought to rest; the same ball is projected from rest so that it moves with a final velocity v; the same ball moving at velocity v is brought to rest and then projrcted backward to its original speed. In which case(s) does the ball undergo the largest change in momentum, |Delta p^rightarrow|? i ii iii both i and ii All are the same

Explanation / Answer

12 By the law of conservation of momentum, total momentum of a system remains conserved if there is no external force acting. Here in this case, no external force is acting. Hence momentum will remain conserved even when it is an inelastic collision. Thus, Final Momentum = -12 -3.5 kg m/s Final momentum = -15.5 kg.m/s Thus correct answer is B. 13 According to the second law of motion, rate of change of momentum is equal to the applied force. Here, same force is exerted to both the bodies. Hence rate of change of momentum will be the same for both. Since initial momentum is also same and final momentum (equal to zero) is also same. Thus both bodies will take the same time to stop. Thus correct answer is B 14 Since the ball bounces off with the same speed and angle, it means that it is an elastic collision and the surface is frictionles. Since the surface is frictionless, the only impulse acting on the ball is due to normal force which is perpendicular to the surface. Thus the direction of the impulse is along the normal to the surface which is along the negative x axis. Thus the correct answer is B. 15 For cases i and ii change in momentum is mv, since in both these cases velocity change is made between 0 and v But for the case iii change in momentum is 2mv since the velocity change is made from v to -v. Thus the largest change in momentum is for the case iii. Thus the correct answer is C

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