CHAPTER 2 HOMEWORK
1. (p.39 Ex.9) A horse canters away from its trainer in a straight line, moving 160m away in 17.0s. It then turns abruptly and gallops halfway back in 6.8s. Calculate (a) its average speed and (b) its average velocity for the entire trip, using "away from the trainer" as the positive direction.
2. (p.39 Ex.14) The position of a ball rolling in a straight line is given by x =2.0 - 4.6t + 1.1t2, where x is in meters and t is in seconds. (a) Determine the position of the ball at t =1.0, 2.0, and 3.0s. (b) What is the average velocity over the interval t = 1.0s to t =3.0s? (c) What is its instantaneous velocity at t = 2.0s and at t =3.0s?
3. (p.40 Ex.17) Calculate the average speed and average velocity of a complete round-trip in which the outgoing 200km is covered at 90km/h, followed by a one-hour lunch break, and the return 200km is covered at 50 =km/h.
4. (p.40 Ex.20) A sports car accelerates from rest to 95km/h in 6.2s. What is its average acceleration in m/s2.
5. (p. 40 Ex.28) The position of a body is given by x = At + 6Bt3, where x is in meters and t is in seconds. (a) What are the units of A and B? (b) What is the acceleration as a function of time? (c) What is the velocity and acceleration at t = 5.0s? (d) What is the velocity as a function of time if x = At + Bt-3?
6. (p.40 Ex.33) A world-class sprinter can reach a top speed ( of about 11.5m/s) in the first 15.0m of a race. What is the average acceleration of this sprinter and how long does it take her to reach that speed?
7. (p.41 Ex.38) A car traveling at 95m/h strikes a tree. The front end of the car compresses and the driver comes to rest after traveling 0.80m. What was the average acceleration of the driver during the collision? Express the answer in terms of "g's," where 1.00g = 9.80m/s2.
8. (p.41 Ex.44) An unmarked police car traveling a constant 95km/h is passed by a speeder traveling 140km/h. Precisely 1.00s after the speeder passes, the policeman steps on the accelerator, if the police car's acceleration is 2.00m/s2, how much time passes before the police car overtakes the speeder (assume moving at constant speed)?
9. (p.41 Ex.51) A kangaroo jumps to a height of 2.55m. How long was it in the air before returning to Earth?
10. (p.41 Ex. 58) A stone is thrown vertically upward with a speed of 23.0m/s. (a) How fast is it moving when it reaches a height of 12.0m? (b) How much time is required to reach this height? (c) Why are there two answers to (b)?