Spring 2015 AP Physics 1Week 9 Homework

Test 2 ReviewCutnell & Johnson 8th Ed Problem 10 on Pg 821. Interactive Solution 3.10 at

www.wiley.com/college/cutnell presents a model for solving this problem. The earth moves around the sun in a nearly circular orbit of radius 1.50 × 1011 m. During the three summer months (an elapsed time of 7.89 × 106 s), the earth moves one-fourth of the distance around the sun. (a) What is the average speed of the earth? (b) What is the magnitude of the average velocity of the earth during this period? Ans: 2.99 × 104 m/s, 2.69 × 104 m/s.

Physics 4th Ed by James S Walker.A dragonfly is observed initially at the position r i= (2.00m) x+ (3.50m) y. Three seconds later it is at the position r f=(−3.00m ) x+ (5.50m ) y. What is the dragonfly’s average velocity during this time? Ans: (-1.67 m/s)x + (0.667 m/s) y.

Physics 4th Ed by James S Walker. Problem 36 on Pg 78.3. The blue curves shown in the figure display the constant speed motion of two different particles in the x-y plane. For each of the eight vectors in the figure, state whether it is (a) a position vector (b) a velocity vector, or (c) an acceleration vector.

Week 8 HW — Due on 10/02/15 1

Physics 4th Ed by James S Walker 1. Problem 38 on Pg 79.4. In its daily prowl of the neighborhood, a cat makes a displacement of 120 m due north, followed by a 72-m displacement due west. (a) Find the magnitude and direction of the displacement required for the cat to return home. (b) if instead, the cat had first prowled 72 m west and then 120 m north, how would this affect the displacement needed to bring it home? Explain.

Physics 4th Ed by James S Walker 1. Problem 39 on Pg 79.5. If the cat in problem 38 takes 45 minutes to complete the 120-m displacement and 17 minutes to complete the 72-m displacement, what are the magnitude and direction of average velocity during this 62-minute period of time?

Cutnell & Johnson 8th Ed Problem 9 on Pg 826. A skateboarder, starting from rest, rolls down a 12.0-m ramp. When she arrives at the bottom of the ramp her speed is 7.70 m/s. (a) Determine the magnitude of her acceleration, assumed to be constant. (b) If the ramp is inclined at 25.0° with respect to the ground, what is the component of her acceleration that is parallel to the ground? Ans: 2.47 m/s2, 2.24 m/s2.

Week 8 HW — Due on 10/02/15 2

Cutnell & Johnson 8th Ed Problem 45 on Pg 847. The lob in tennis is an effective tactic when your opponent is near the net. It consists of lofting the ball over his head, forcing him to move quickly away from the net (see the drawing). Suppose that you lob the ball with an initial speed of 15.0 m/s, at an angle of 50.0° above the horizontal. At this instant your opponent is 10.0 m away from the ball. He begins moving away from you 0.30 s later, hoping to reach the ball and hit it back at the moment that it is 2.10 m above its launch point. With what minimum average speed must he move? (Ignore the fact that he can stretch, so that his racket can reach the ball before he does.) Ans: 5.80 m/s

Week 8 HW — Due on 10/02/15 3