Physics 011

A of PQ#6A

Chapter 6: Work and Energy
Practice Questions

1.	Two men, Joel and Jerry, push against a wall. Jerry stops after 10 min, while Joel is able to push for 5 min longer. Compare the work against the wall they each do. The correct answer: Neither of them do any work. The formula for work does not involve the time. Review Section 6-1 in Giancoli.
2.	Which of the following graphs illustrates Hooke's Law (the spring force)? The correct answer: Review Section 6-4 in Giancoli.
3.	A simple pendulum, consisting of a mass m and a string, swings upward, making an angle q with the vertical. The work done by the tension force is The correct answer: zero.
4.	What is the mass of the pendulum 'bob' in the figure? The correct answer: 1 kg The potential energy is mgh. Review Section 6-4 in Giancoli.
5.	What is the total mechanical energy, ME, of the pendulum?
6.	What is the maximum kinetic energy of the pendulum? The correct answer: 9.8 J This is the minimum kinetic energy. Review Section 6-7 in Giancoli.
7.	What is the potential energy, PE, at point B and D? The correct answer: 4.9 J This would be the energy at the top. Review Section 6-7 in Giancoli.
8.	At point B and D what is the relationship between the kinetic energy, KE and the potential energy, PE? The correct answer: KE=PE KE+PE=constant. Review Section 6-7 in Giancoli.
9.	What is the speed of the pendulum at point B and D? The correct answer: 3.1 m/s That is the speed at the top. Review Section 6-7 in Giancoli.
10.	What is the speed of the pendulum at point C? The correct answer: 4.4 m/s
11.	A simple pendulum, consisting of a mass m, is attached to the end of a 1.5 m length of string. If the mass is held out horizontally, and then released from rest, its speed at the bottom is
12.	A 4-kg mass moving with speed 2 m/s, and a 2-kg mass moving with a speed of 4 m/s, are gliding over a horizontal frictionless surface. Both objects encounter the same horizontal force, which directly opposes their motion, and are brought to rest by it. Which statement best describes their respective stopping distances? The correct answer: The 2-kg mass travels twice as far as the 4-kg mass before stopping. The work (W=F*D) equals the change in kinetic energy. Review Example 6-5 in Giancoli.
13.	A 4-kg mass moving with speed 2 m/s and, an otherwise identical, 2-kg mass moving with a speed of 4 m/s, are gliding over a horizontal surface with friction and are brought to rest by it. Which statement best describes their respective stopping distances? Your answer: The 2-kg mass travels greater than twice as far.
14.	A force that object A exerts on object B is observed over a 10-second interval, as shown on the graph. How much work did object A do during that 10 s? The correct answer: 25 J The force is always positive (in the direction of motion). Review Section 6-4 in Giancoli.
15.	A force that object A exerts on object B is observed over a 10-second interval, as shown on the graph. What is the average power output of A into B? The correct answer: 2.5 W Review Section 6-10 in Giancoli.
16.	The resultant force you exert on a shopping cart, for a 10 s period, is plotted on the graph, shown. How much work did you do during this 10 s interval? The correct answer: Zero This would be the work if both forces were below the x-axis. Review Section 6-4 in Giancoli.
17.	The resultant force you exert on a shopping cart, for a 10 s period, is plotted on the graph, shown. Which of the following statements are true? The correct answer: The average power is zero. Review Section 6-10 in Giancoli.
18.	How much work was required to bring the 1000-kg roller coaster from point P to rest at point Q at the top of the 50 m peak? The correct answer: 490,000 J
19.	If the roller coaster leaves point Q from rest, how fast is it traveling at point R? The correct answer: 31.3 m/s Don't forget that there is a 1/2. Review Section 6-7 in Giancoli.
20.	If the roller coaster leaves point Q from rest, what is its speed at point S (at the top of the 25-m peak) compared to its speed at point R? The correct answer:
21.	What was the total work done on you by all the forces in the universe between the time just before you awoke this morning and right now? The correct answer: Zero. Review Section 6-3 in Giancoli.
22.	Two cars, starting from rest at the same place, travel by different routes to the same destination. One of the cars passes the other as they drive through it. Which of the following statements will be true? The correct answer: The work done by gravity is the same on both.
23.	The work done by friction, f, The correct answer: equals -fd, where d is the total distance moved. The angle is always 180 degrees. Review Section 6-1 in Giancoli.
24.	A 102 kg man climbs a 5.0 meter high stair case at constant speed How much work does he do? The correct answer: 5000 J You probably forgot 'g'. Review Section 6-4 in Giancoli.
25.	A ball is released, from rest, at the left side of the loop-the-loop, at the height shown. If the radius of the loop is R and there is no friction, what vertical height does the ball rise to on the other side? (LOOP-THE-LOOP) The correct answer: 2R