Physics Practice Test
Practice Final: Your Final will consist of MC, TF and Problems. If you correctly work the problems and answer the essay questions on this test you should be prepared.
1. Equilibrium occurs when
2. A girl whose weight is 500 N hangs from the middle of a bar supported by two vertical strands of rope. What is the tension in each strand?
3. The weight of a person can be represented by a vector that acts
4. What would be the safest way to put up a clothesline?
5. A barge is being pulled along a canal by two ropes that make equal angles with the direction in which the barge points. Assuming the two pulls on the barge are equal, in what direction does the barge move?
6. A 100-N lantern is suspended by a pair of ropes with 120 degrees between them (each 60 degrees from the vertical). The tension in each rope is
7. You are helping your aunt move a piano on wheels from one room to another. When you push the piano horizontally, it moves at constant speed. What can you say about the piano?
8. In order to find the components of a vector, you should
9. In physics, work is defined as
10. If you lift two loads up one story, how much work do you do compared to lifting just one load up one story?
11. The unit of work is the
12. Power is defined as the
13. The unit of power is the
14. Potential energy is the energy an object has because of its
15. The amount of potential energy possessed by an elevated object is equal to
16. Kinetic energy of an object is equal to
17. An arrow in a bow has 70 J of potential energy. Assuming no loss of energy to heat, how much kinetic energy will it have after it has been shot?
18. A ball is thrown into the air with 100 J of kinetic energy, which is transformed to gravitational potential energy at the top of its trajectory. When it returns to its original level after encountering air resistance, its kinetic energy is
19. An object that has kinetic energy must be
20. An object that has kinetic energy must have
21. An object at rest may have
22. How many joules of work are done on a box when a force of 25 N pushes it 3 m?
23. How much power is required to do 40 J of work on an object in 5 seconds?
Essay
24. Briefly distinguish between vectors and scalars, giving examples of each.
vectors have magnitude and direction where as scalars only have magnitude.
An example of a vector is velocity and an example of a scalar is mass.
25. Write a short paragraph about what the early scientists from Aristotle to Galileo thought about the nature of motion.
26. State the law of inertia in its full form and give examples of how it works.
The law of inertia states that an object that is in motion will stay in motion unless another force is acted upon it and an object at rest will stay at rest until acted upon an opposite force. For example a soccer ball will stay still on the ground until the force of someone kicking it and it will keep moving until the force of friction of the grass stops it.
27. Write a short paragraph on the difference between mass and weight. Give examples.
Mass is the amount of matter in an object and is measured in kilgrams. Weight is the amount of gravitational force exerted on the objects mass and is measured in newtons. So the mass of block could be 5kg and would stay the same no matter the location, but an object on the moon has a different weight than on the earth becuase the gravitational force is different.
28. Suppose you are on an airplane moving at high speed. If you flip a coin straight up it will land in your lap rather than a great distance behind you. Explain.
29. Write a short paragraph explaining the difference between speed and velocity, and give examples of both.
Speed is a scalar quantity meaning it only has magnitude where as velocity has both magnitude and direction. For example speed is measured in time such as 5 m/s but velocity is the division of time and distance such as 4m/s².
30. Write a short paragraph explaining what acceleration is and why a car is accelerating as it rounds a corner.
Acceleration is the change in an objects velocity. When a car is going at constant velocity and is about to round a corner the direction changes therefore the velocity changes and so the acceleration is decreasing.
31. Write a short paragraph on how fast things fall on Earth. Compare this to motion on the moon, where the acceleration due to gravity is about 1.6 m/s2.
On earth the accaleration due to gravity is about 10 m/s² which means the fall of an object on earth would be gaining 10 m/s each second where as on the moon things fall with a slower speed of 1.6m/s every second
32. Use the parallelogram method and some graph paper to find the resultant of a 12-unit vector and a 16-unit vector that are at angles of 30 degrees, 90 degrees, 135 degrees, and 180 degrees from each other.
33. On a piece of graph paper, draw lines 17 cm long at angles of 0 degrees, 30 degrees,
90 degrees, and 135 degrees from the x-axis. Find the x- and y- components of each line.
34. A plane flies north at 230 km/h. At the same time, there is wind of 80 km/h from the west. Use both a scaled diagram and the Pythagorean Theorem to find the resultant velocity of the plane. How closely do your answers agree?
35. Figure 3.9 in the text shows two balls released simultaneously from a mechanism that allows one ball to drop freely while the other is projected horizontally. Explain why the balls fall farther and farther each successive time interval. Explain why the projected ball has the same vertical location as the falling ball.
36. Explain why the acceleration of two freely-falling objects having different masses is the same. Is the force on each mass the same?
37. What two things does the force of friction depend on? In which direction does friction act? What would happen if friction were to act in the same direction as the motion?
38. What is terminal speed? When a skydiver has reached terminal speed, what is the air resistance equal to? What is the skydiver's acceleration?
39. In terms of momentum change, explain why it is best to "give" when catching a baseball. Provide other examples of situations in which you want to lengthen the impact time in a collision.
40. What does it mean to say that momentum is conserved? Give at least two examples where momentum is conserved in a collision.
41. A railroad diesel engine coasting at 12 km/h runs into a stationary flatcar. The diesel weighs 5 times as much as the flatcar. Assuming the cars couple together, how fast are they moving after the collision?
Problem
42. What is the magnitude of the resultant of a 6.0-N force acting vertically upward and a 4.0-N force acting horizontally?
7.2
43. A 230.0 kg bear grasping a vertical tree slides down at constant velocity. What is the friction force between the tree and the bear?
2254
44. Two forces of 10 N both act on an object. The angle between the forces is 90°. What is the magnitude of their resultant?
14
45. The following forces act on an object: 9 N north, 52 N south, and 55 N west. What is the magnitude of the net force?
69.8
46. How much (in Newton’s) does a 10.0-kg bag of grass seed weigh?
98
47. A person weighs 650 N. What is the mass of the person?
65
48. On the surface of Jupiter, the acceleration due to gravity is about 3 times that on Earth. How much would a 0.40-kg rock weigh on Jupiter?
12
49. On the surface of Jupiter, the acceleration due to gravity is about 3 times that of Earth. What would be the mass of a 170-kg rock on Jupiter?
170
50. What is the average speed of a cheetah that runs 88 m in 5 seconds?
17.6 m/s
51. What is the average acceleration of a car that goes from rest to 60 km/h in 8 seconds?
7.5 km/hXs
52. A jet on an aircraft carrier can be launched from 0 to 40 m/s in 2 seconds. What is the acceleration of the jet?
20 m/s²
53. A skateboarder starting from rest accelerates down a ramp at 2 m/s2 for 2 s. What is the final speed of the skateboarder?
4m/s
54. An apple falls from a tree and 0.5 second later hits the ground. How fast is the apple falling when it hits the ground?
5m/s
55. What speed must you toss a ball straight up so that it takes 4 s to return to you?
20m/s
56. You toss a ball at 5 m/s straight upward. How much time will the ball take to reach the top of its path?
.5
57. How much time does a car with an acceleration of 5 m/s2 take to go from 5 m/s to 40 m/s?
7s
58. A crate falls from an airplane flying horizontally at an altitude of 1250 m. Neglecting air drag, how long will the crate take to strike the ground?
59. A stone is dropped from a cliff. After it has fallen 10 m, what is the stone's velocity?
60. A motorboat is driven across a river at 3.0 km/h at right angles to a current that is flowing at 10.0 km/h. What is the resulting speed of the motorboat?
61. A package falls out of a helicopter that is traveling horizontally at 70 m/s. It falls into the water below 8.0 seconds later. Assuming no air resistance, what is the horizontal distance it travels while falling?
62. Kyle throws a ball horizontally from the top of a building that is 5.0 m high. He hopes the ball will reach a swimming pool that is at the bottom of the building, 12.0 m horizontally from the edge the building. If the ball is to reach the pool, with what initial speed must Kyle throw it with?
63. An airplane whose airspeed is 295 km/h flies parallel to the direction of a wind with a speed of 40.0 km/h. What are the two possible speeds of the plane relative to the ground?
64. A ball is thrown horizontally from the top of a tall cliff. Neglecting air drag, what vertical distance has the ball fallen 2.0 seconds later?
65. A snowball rolls off the edge of a horizontal roof at a velocity of 3.0 m/s. What is the speed of the snowball 1.0 s later?
66. You push with 10.0 N on a 5.0-kg block and there are no opposing forces. How fast will the block accelerate?
67. You push with 27 N on a 10-kg chest, and there is a 7-N force of friction. How fast will the chest accelerate?
68. A 400,000-kg airplane in takeoff uses the 40,000 N thrust of each one of its four engines. What is the acceleration of the plane during takeoff?
69. An unbalanced force of 30 N gives an object an acceleration of 6.0 m/s2. What force would be needed to give it an acceleration of 1.0 m/s2?
70. A net force of 1.0 N acts on a 4.0-kg object, initially at rest, for 4.0 seconds. What is the distance the object moves during that time?
71. When air resistance on a falling skydiver builds up to 0.3 the weight of the skydiver, what is the acceleration of the skydiver?
72. Suppose that you exert 300 N horizontally on a 50-kg crate on a factory floor, where friction between the crate and the floor is 100 N. What is the acceleration of the crate?
73. A 20-kg block of cement is pulled upward (not sideways!) with a force of 400 N. What is the acceleration of the block?
74. Bronco the skydiver, who’s mass is 80 kg experiences 200 N of air resistance. What is the acceleration of his fall?
75. What is the average momentum of a 50-kg skateboarder who covers 400 m in 50 s?
76. A cement truck with a mass 16,000 kg moving at 15 m/s slams into a cement wall and comes to a halt. What is the force of impact on the truck?
77. A 10-kg cement block moving horizontally at 6 m/s plows into a bank of sand and comes to a stop in 2 s. What is the average impact force on the bank?
78. An 8-kg blob of clay moving horizontally at 2 m/s hits a 3-kg blob of clay at rest. What is the speed of the two blobs stuck together immediately after the collision?
79. A 10-kg bowling ball moving at 4 m/s bounces off a spring at about the same speed that it had before bouncing. What is the change in momentum of the bowling ball?
80. A 50-kg cart moving at 100 km/h collides head-on with an approaching 50-kg cart moving at 10 km/h (in the opposite direction). If the two carts stick together, what will be their speed?
81. A 30-kg girl and a 50-kg boy face each other on friction-free roller skates. The girl pushes the boy, who moves away at a speed of 3 m/s. What is the girl's speed?
82. A 70-kg free-floating astronaut fires 0.10-kg of gas at a speed of 30 m/s from her propulsion pistol. What is the astronaut's recoil speed?
83. Assume that a 15-kg ball moving at 8 m/s strikes a wall perpendicularly and rebounds elastically at the same speed. What is the amount of impulse given to the wall?
More chapter 9 questions located after the answer section
MULTIPLE CHOICE
1. ANS: E OBJ: 2.2 Mechanical Equilibrium KEY: equilibrium | force
2. ANS: B OBJ: 2.2 Mechanical Equilibrium KEY: weight | tension
3. ANS: D OBJ: 2.2 Mechanical Equilibrium KEY: weight | vector
4. ANS: C OBJ: 2.3 Support Force KEY: tension | clothesline
5. ANS: E OBJ: 2.3 Support Force KEY: resultant | force
6. ANS: C OBJ: 2.3 Support Force KEY: tension | rope
7. ANS: B OBJ: 2.4 Equilibrium for Moving Objects KEY: equilibrium | dynamic equilibrium | static equilibrium
8. ANS: D OBJ: 2.5 Vectors KEY: vector | magnitude
9. ANS: E OBJ: 9.1 Work KEY: work | force | distance
10. ANS: D OBJ: 9.1 Work KEY: load | work
11. ANS: C OBJ: 9.1 Work KEY: work | joule
12. ANS: C OBJ: 9.2 Power KEY: power | work | time
13. ANS: E OBJ: 9.2 Power KEY: power | watt
14. ANS: C OBJ: 9.4 Potential Energy KEY: potential | energy
15. ANS: D OBJ: 9.4 Potential Energy KEY: potential | energy
16. ANS: B OBJ: 9.5 Kinetic Energy KEY: kinetic | energy
17. ANS: D OBJ: 9.6 Work-Energy Theorem KEY: potential | energy | kinetic
18. ANS: C OBJ: 9.6 Work-Energy Theorem KEY: kinetic | energy | potential
19. ANS: C OBJ: 9.5 Kinetic Energy KEY: kinetic | energy
20. ANS: C OBJ: 9.5 Kinetic Energy KEY: kinetic | energy
21. ANS: A OBJ: 9.4 Potential Energy KEY: rest | energy
22. ANS: E OBJ: 9.1 Work KEY: joule | work | force
23. ANS: C OBJ: 9.2 Power KEY: power | work | time
ESSAY
24. ANS: OBJ: 2.5 Vectors KEY: vector | scalar
A vector is a quantity that has direction and magnitude; a scalar has only magnitude. Force, velocity, acceleration, and weight are all vectors. Mass, time, temperature, and speed are scalars.
25. ANS:
Aristotle thought there were two kinds of motion—natural and violent. Natural motion referred to things falling and moving through space. Violent motion referred to motion under imposed forces. Copernicus thought that Earth moves around the sun. Galileo developed the modern ideas of force and inertia. Force is needed to change motion.
OBJ: 3.1 Aristotle on Motion | 3.2 Copernicus and the Moving Earth | 3.3 Galileo on Motion
KEY: Aristotle | Galileo | motion
26. ANS: The law of inertia says that an object in motion will continue in its state of motion unless an outside force acts on it. This means that a book at rest on a table will stay at rest on the table until someone or something picks it up, bumps it, or in some other way forces it to move. It also means that once we throw a ball in deep space, the ball will continue in a straight line until it runs into something.
OBJ: 3.5 Mass-A Measure of Inertia
27. ANS:
Mass generally refers to the quantity of matter in an object, whereas weight is the force due to gravity on an object. The mass of an object is the more basic quantity, for it is the same regardless of gravity. For example, a 1-kg brick has a mass of 1 kg on Earth, 1 kg on the moon, and 1 kg in deep space. Its weight, however, is 10 N on Earth, 1.6 N on the moon, and 0 N in deep space.
OBJ: 3.5 Mass-A Measure of Inertia KEY: mass | weight
28. ANS:
You, the coin, and the air are all moving horizontally at the same speed. When you flip a coin into the air, it will continue moving horizontally at that speed (Newton's first law).
OBJ: 3.6 The Moving Earth Again KEY: Newton | velocity
29. ANS:
Speed is the rate at which an object covers distance. Velocity is speed in a direction. When you get in a car and travel on a highway at 90 km/hr that is your speed. If you are traveling south, then your velocity is 90 km/h S.
OBJ: 4.3 Velocity KEY: speed | velocity
30. ANS:
Acceleration is the rate of change of velocity. Since velocity has both speed and direction, if the direction of a moving object changes, as in rounding a corner, then the object is accelerating.
OBJ: 4.4 Acceleration KEY: acceleration | change
31. ANS:
The acceleration due to gravity on Earth is 10 m/s2. On the moon, it is roughly one sixth of that, or 1.6 m/s2. This means that when an object falls straight down on Earth, it gains 10 m/s of speed in each second. On the moon it gains a speed of 1.6 m/s each second.
OBJ: 4.5 Free Fall: How Fast? KEY: gravity | Earth | moon
32. ANS:
Assuming the 12-unit vector lies along the x-axis and the 16-unit vector along the y-axis, the correct answers are 27.1 units at 17.2 degrees, 20 units at 53.2 degrees, 11.3 units at 86.6 degrees, and 4 units at 180 degrees.
OBJ: 5.2 Velocity Vectors KEY: resultant | angle | vector
33. ANS:
The x- and y-components of the vector are 0 degrees: x = 17 cm, y = 0 cm; 30 degrees: x = 14.7 cm, y = 8.5 cm; 90 degrees: x = 0 cm, y = 17 cm; 135 degrees: x = –12 cm, y = 12 cm.
OBJ: 5.3 Components of Vectors KEY: vector | angle
34. ANS:
Resultant velocity of the plane is the square root of (2302 + 802) km/h which equals 244 km/h. In general, the graphical method will not be as precise as the analytical method. However, the answers should be within a few percent of each other.
OBJ: 5.2 Velocity Vectors KEY: Pythagorean Theorem | vector
35. ANS:
One ball is projected from the top of a table with horizontal velocity. Another ball is dropped from the same starting location. Both balls hit the ground at the same time. Both balls fall the same distance in the same time interval, the only difference being that the projected ball travels horizontally at the same time the vertical motion takes place. Motion in one direction is independent of motion in the other direction. The only thing in common between the two motions is the length of time they are falling. The only force on each ball is the force of gravity, which accelerates the balls only downward.
OBJ: 5.4 Projectile Motion KEY: projectile | gravity
BLM: analysis
36. ANS:
Newton's second law, a = F / m reminds us that the acceleration of an object depends on two things: the force that acts on it and the object's mass. The force that acts on a freely falling object is the force of gravity—its weight. It would seem that the greater the weight, the greater should be the acceleration of the fall. However, the mass of the object resists acceleration. This is inertia. The force of gravity is greater on the more massive object, but its inertia is correspondingly greater. This results in the same ratio of force to mass for the two falling objects. Hence their accelerations are the same.
OBJ: 6.6 Free Fall Explained KEY: acceleration | mass
37. ANS:
Friction depends on the nature of the two surfaces that are in contact and also on how much force is pushing the two surfaces together. It always acts in a direction to oppose motion. If it didn't, then once we started an object sliding, it would move faster and faster and never stop, until it ran out of surface or ran into something!
OBJ: 6.4 Friction KEY: force | friction
38. ANS:
Terminal speed is the maximum speed of an object when it falls through a fluid. A skydiver will reach terminal speed when the force of air friction equals his or her weight. At that point the weight of the diver and the force of air friction on the diver are balanced, the net force is zero, and he or she falls with no acceleration (i.e. constant speed).
OBJ: 6.7 Falling and Air Resistance KEY: terminal speed | resistance
39. ANS:
The force of impact in catching a ball will be less if the time of impact is lengthened. Other situations in which you want to lengthen the time of impact might be in a car or bicycle collision, in catching a soccer ball, and in hitting a baseball (to give it the most momentum you can).
OBJ: 8.2 Impulse Changes Momentum KEY: momentum | time | collision
40. ANS:
Conservation of momentum means that in a given system and situation where no external forces are acting, net momentum is neither created nor destroyed. For example, momentum is conserved in collisions and explosions, where the forces that act are internal. When a firecracker bursts, the momentum of its fragments add up to the firecracker’s momentum just before bursting. On the other hand, when you drop a rock, the momentum of the rock changes because the force of gravity acts on it; however, if you consider the rock and Earth as one system, then Earth and the rock each acquire the same amount of momentum, but in opposite directions, so the total momentum of the system is and remains zero.
OBJ: 8.4 Conservation of Momentum KEY: momentum | conserve | collision
41. ANS:
Momentum before the collision = mass of engine times 12 km/h. Momentum after the collision = times mass of engine times v. Equating the two expressions, and solving for v gives, v = (12 km/hr) () = 10 km/hr
OBJ: 8.5 Collisions KEY: weight | motion
PROBLEM
42. ANS: 7.2 N OBJ: 2.1 Force KEY: magnitude | force
43. ANS: 2254 N OBJ: 2.2 Mechanical Equilibrium KEY: velocity | friction
44. ANS: 14 N OBJ: 2.3 Support Force KEY: force | resultant
45. ANS: 70 N OBJ: 2.3 Support Force KEY: force | magnitude
46. ANS: 100 N OBJ: 3.5 Mass-A Measure of Inertia KEY: weight |Newton’s
47. ANS: 65 kg OBJ: 3.5 Mass-A Measure of Inertia KEY: mass | weight
48. ANS: 12 N OBJ: 3.5 Mass-A Measure of Inertia KEY: gravity | weight
49. ANS: 170 kg OBJ: 3.5 Mass-A Measure of Inertia KEY: gravity | weight
50. ANS: 17.6 m/s OBJ: 4.2 Speed KEY: average | speed
51. ANS: 7.5 km/h·s OBJ: 4.4 Acceleration KEY: average | acceleration
52. ANS: 20 m/s2 OBJ: 4.4 Acceleration KEY: acceleration
53. ANS: 4 m/s OBJ: 4.4 Acceleration KEY: acceleration | speed
54. ANS: 5 m/s OBJ: 4.6 Free Fall: How Far? KEY: acceleration | speed
55. ANS: 20 m/s OBJ: 4.6 Free Fall: How Far? KEY: speed | acceleration
56. ANS: 0.5 s OBJ: 4.6 Free Fall: How Far? KEY: acceleration | speed
57. ANS: 7 s OBJ: 4.4 Acceleration KEY: acceleration | time
58. ANS: 15.8 s OBJ: 4.7 Graphs of Motion KEY: gravity | acceleration
59. ANS: 14 m/s OBJ: 4.6 Free Fall: How Far? KEY: velocity | gravity
60. ANS: 10.4 km/h OBJ: 5.2 Velocity Vectors KEY: speed | resultant
61. ANS: 560 m OBJ: 5.4 Projectile Motion KEY: vector | resistance
62. ANS: 12.0 m/s OBJ: 5.6 Projectiles Launched at an Angle KEY: projectile | speed
63. ANS: 255 and 335 km/h OBJ:5.2 Velocity Vectors KEY: vector | speed
64. ANS: 20 m OBJ: 5.6 Projectiles Launched at an Angle KEY: projectile | vertical
65. ANS: 10.4 m/s OBJ: 5.4 Projectile Motion KEY: speed | velocity
66. ANS: 2.0 m/s2 OBJ: 6.3 Newton's Second Law of Motion KEY: force | acceleration
67. ANS: 2 m/s2 OBJ: 6.3 Newton's Second Law of Motion KEY: force | friction | acceleration
68. ANS: 0.4 m/s2 OBJ: 6.3 Newton's Second Law of Motion KEY: thrust | acceleration
69. ANS: 5.0 N OBJ: 6.3 Newton's Second Law of Motion KEY: force | acceleration
70. ANS: 2.0 m OBJ: 6.3 Newton's Second Law of Motion KEY: net force | distance
71. ANS: 7 m/s2 OBJ: 6.7 Falling and Air Resistance KEY: resistance | acceleration
72. ANS: 4 m/s2 OBJ: 6.7 Falling and Air Resistance KEY: force | friction | acceleration
73. ANS: 10 m/s2 OBJ: 6.6 Free Fall Explained KEY: force | acceleration
74. ANS: 7.5 m/s2 OBJ: 6.7 Falling and Air Resistance KEY: resistance | acceleration
75. ANS: 400 kg·m/s OBJ: 8.1 Momentum KEY: momentum
76. ANS: Not enough information to say. OBJ: 8.2 Impulse Changes Momentum KEY: impact
77. ANS: 30 N OBJ: 8.2 Impulse Changes Momentum KEY: force
78. ANS: 1.5 m/s OBJ: 8.5 Collisions KEY: speed | collision
79. ANS: 80 kg·m/s OBJ: 8.2 Impulse Changes Momentum KEY: speed | momentum
80. ANS: 45.0 km/h OBJ: 8.5 Collisions KEY: speed | collision
81. ANS: 5.0 m/s OBJ: 8.4 Conservation of Momentum KEY: speed
82. ANS: 0.04 m/s OBJ: 8.4 Conservation of Momentum KEY: speed | recoil
83. ANS: 240 N·s OBJ: 8.2 Impulse Changes Momentum KEY: elastic | speed
POP Chapter 9
Essay
1. You do work on something when you lift it against gravity. How does this work relate to gravitational potential energy? If the lifted object is released, what becomes of this energy? Be sure to define all terms that you use.
2. Discuss how energy conservation applies to a pendulum. Where is potential energy the most? The least? Where is kinetic energy the most? The least? Where is it moving the fastest? Stopped?
Problem
3. What is the work done in lifting 60 kg of blocks to a height of 20 m?
4. A toy cart moves with a kinetic energy of 10 J. If its speed is doubled, what will its kinetic energy be?
5. What amount of work can a 600-W motor do in 4 minutes?
6. A 30-kg girl runs up the staircase to a floor 5 m higher in 8 seconds. What is her power output?
7. The 4.0-kg head of an ax is moving at 4.0 m/s when it strikes a log and penetrates 0.01 m into the log. What is the average force the blade exerts on the log?
Answer Section
ESSAY
1. ANS:
The work you do when lifting something may be stored as gravitational potential energy. Then the force times the distance is equal to the weight times the height. If the lifted object is released, this energy transforms to motion energy (or kinetic energy). The kinetic energy as it returns to its starting point equals the gravitational potential energy at its highest point, which in turn equals the work done on it in the first place.
OBJ: 9.6 Work-Energy Theorem KEY: work | gravity
2. ANS:
Net energy is never created or destroyed. It can change from one form to another form. A swinging pendulum has the most gravitational potential energy at the top of its swing. At that point it has no kinetic energy. At the bottom of its swing its potential energy is at a minimum, or zero relative to that lowermost point, and its kinetic energy is at a maximum. Halfway down, it has half kinetic and half potential energy. Everywhere along the swing the sum of the kinetic and potential energies is the same. When air resistance and friction are taken into account, energy is transferred from the pendulum to the surroundings in the form of heat.
OBJ: 9.6 Work-Energy Theorem KEY: pendulum | conservation
PROBLEM
3. ANS: 12,000 J
OBJ: 9.1 Work KEY: work
4. ANS: 40 J
OBJ: 9.5 Kinetic Energy
STA: SCSh5.e| SCSP3| SCSP3.a KEY: kinetic | energy | speed
5. ANS: 144,000 J
OBJ: 9.2 Power KEY: work | time
6. ANS: 188 W
OBJ: 9.2 Power KEY: mass | power
7. ANS: 3200 N
OBJ: 9.5 Kinetic Energy KEY: force