Chapter 2

  1. (p.42 Prob.71) A person who is properly constrained by an over-the-shoulder seat belt has a good chance of surviving a car collision if the deceleration does not exceed 30"g's" (1.00g = 9.80m/s2). Assuming uniform deceleration of this value, calculate the distance over which the front end of the car must be designed to collapse if a crash brings the car to rest  from 100km/h.

    Answer.

  2. (p.43 prob.74) Figure 2-40 is a position versus time graph for the motion of an object along the x axis. As the object moves from A to B: (a) Is the object moving in the positive or negative direction? (b) Is the object speeding up of slowing down? (c) Is the acceleration of the object positive or negative? Next for the time interval from D to E: (d) Is the object moving in the positive or negative direction? (e) Is the object speeding up of slowing down? (f) Is the acceleration of the object positive or negative? (g) Finally, answer these same three questions for the time interval from C to D.

    3. Answer.

  3. (p.43 prob.78) A police car at rest, passed by a speeder traveling at a constant 110km/h, take off in hot pursuit. The police officer catches up to the speeder in 700m, maintaining a constant acceleration. (a) Qualitatively plot the position versus time graph for both cars from the police car's start to the catch-up point. (b) Calculate how long it took the police officer to overtake the speeder, (c) calculate the required police car acceleration, and (d) calculate the speed of the police car at the overtaking point.

    Answer.

     

  4. (p.44 prob.83) A stone is thrown vertically upward with a speed of 10.0m/s from the edge of a cliff 65.0m high (Fig. 2-43). (a) How much later does it reach the bottom of the cliff? (b) What is its speed just before hitting? (c) What total distance did it travel?

        Answer.

  

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