Physics 011

Chapter 2

Answers of PQ#2

1.	Figure 2-1 At t = 0 s The correct answer: rider D is ahead of rider C. See Section 2-8 in Giancoli
2.	Figure 2-1 At t = 0 s The correct answer: C and D are both moving. See Section 2-8 in Giancoli.
3.	Figure 2-1 At t = 0 s The correct answer: C has a greater velocity than D.
4.	Figure 2-1 At t = 10 s The correct answer: C and D are at the same position.
5.	Figure 2-2 During the first 8 s The correct answer: C has decreasing velocity and D has increasing velocity.
6.	Figure 2-2 During the first 8 s The correct answer: their accelerations are equal in magnitude but opposite in sign. The slopes are the same. Review Section 2-8 in Giancoli.
7.	Figure 2-2 Based on all the graphical information The correct answer: not enough information is given to decide if they meet. Review Section 2-5 in Giancoli.
8.	Which graph represents an object at rest? The correct answer:
9.	Which graph represents constant positive acceleration? The correct answer: This slope is zero. Review Section 2-5 in Giancoli.
10.	How is motion in the negative x direction represented on an x vs. t plot? The correct answer: By a downward sloping curve. Velocity is the slope of the curve. Review Section 2-8 in Giancoli.
11.	What is the meaning of a horizontal line on a plot of v vs. t? The correct answer: The object is moving at constant speed. See Section 2-8 in Giancoli.
12.	If a car accelerates from rest in the positive direction The correct answer: its initial velocity is zero. If it is accelerating its final speed is greater than its initial speed. Review Section 2-5 in Giancoli.
13.	A car accelerating from rest at 2.0 m/s^2 for 5 s The correct answer: has a final speed of 10 m/s. Review Section 2-5 in Giancoli.
14.	In this problem "up" is taken to be positive. A ball is dropped off a high cliff Your answer: and its initial velocity is zero.
15.	In this problem "up" is taken to be positive. A ball is thrown straight up in the air, at the very top its The correct answer: its acceleration is -9.8 m/s^2 The velocity must be zero at the top. See Example 2-14 in Giancoli.
16.	In this problem "up" is taken to be positive. A vertically upward thrown rock has a The correct answer: positive initial velocity.
17.	In this problem "up" is taken to be positive. A falling object has The correct answer: negative acceleration and negative velocity. See example 2-14 in Giancoli.
18.	In this problem "up" is taken to be positive. An object moving upward under the influence of gravity has The correct answer: negative acceleration and positive velocity. See example 2-14 in Giancoli.
19.	In this problem "up" is taken to be positive. A ball thrown vertically upward with an initial velocity of 19.6 m/s, after 5 s has a final velocity of The correct answer: -29.4 m/s. Review Section 2-7 in Giancoli.
20.	An object is shot upward at 34.3 m/s. How high does it go? Your answer: 60.0 meters
21.	Ball A is thrown vertically upward with a speed of 19.6 m/s from the top edge of a high building. As it passes the edge on the way down, a second ball, B, is thrown downward at 19.6 m/s. Which of the following is correct? The correct answer: The two balls hit the ground at the same time. See Example 2-15 in Giancoli.
22.	A car moving right to left applies the brakes. Its The correct answer: velocity is negative and its acceleration is positive. Since it is moving to the left its velocity must be negative. Review Section 2-6 in Giancoli.
23.	A ball is dropped off a ledge. How far does it fall in the 2nd second? The correct answer: 14.7 meters That is how far it falls in 1 second. Review Section 2-7 in Giancoli.
24.	Ball A is thrown upward at the same time as ball B and with half the speed of ball B. Which of the following is true? The correct answer: A will hit before B. Review Example 2-13 in Giancoli.
25.	Ball A is thrown upward at the same time as ball B and with half the speed of ball B. How much higher does B go than A? The correct answer: 4 times. See example 2-13 in Gian