Phys 107 Final Exam

58. A jack system will increase the potential energy of a heavy load by 400 J and generate 600 J of heat with a work input of 1000 J. The efficiency of the jack system is

40%

83. A metal block has a density of 5000 kg per cubic meter and a volume of 2 cubic meters. What is the block's mass?

10,000 kg

73. If each dimension of a steel bridge is scaled up ten times, its strength will be multiplied by about

100, but its weight by 1,000

22. A tow truck exerts a force of 3000 N on a car, accelerating it at 3 meters per second. What's the mass of the car?

1000 kg

29. How much pushing force is needed to accelerate a 50 kg desk at 1 m/s squared across the floor if the friction force is 70 N?

120 N

43. A car moving at 50 km/hr skids 20 m with locked brakes. How far will the car skid with locked brakes if it were traveling at 150 km/hr?

180 m

66. Do 100 J of work in 50 s and your power output is

2 W

97. What is the approximate weight of the air in an empty standard-sized refrigerator?

2-3 pounds

62. To tighten a bolt, you push with a force of 80 N at the end of a wrench handle that is ¼ m from the axis of the bolt. Assuming that you push perpendicular to the wrench handle, the torque you are exerting is

20 Nm

27. At one instant an object in free fall is moving upward at 20 meters per second. Four seconds later its speed is about

20 m/s

53. A 1000-kg car moving at 10 m/s brakes to a stop in 5 s. The average braking force is

2000 N

67. A proton is

2000 times more massive than an electron

72. When a living cell doubles in diameter, the amount of its material to be nourished is multiplied by eight, but the amount of membrane through which to feed it is multiplied by

4

19. Which of the following theories was first published by Copernicus? a. heavier objects fall faster b. a force is required to change the motion of an object c. the sun circles the Earth d. None of these

D. none of these (he came up with the Earth circles the Sun)

51. A woman alleviates her back pain in the fifth month of pregnancy by wearing a backpack instead of carrying a purse. When the pain resurfaces in the ninth month of pregnancy, she can reduce the back pain once again by: a. delivering the baby b. walking in snowshoes c. adding a few books to her backpack d. hanging the backpack from the end of a stick carried over her shoulder e. all of the above

E. all of the above

70. Which of the statements is true? a. An atom is the smallest particle known to resist b. There are thousands of different kinds of atoms that account for a wide variety of substances c. Chemical elements are made up of about 100 distinct molecules d. Molecules form atoms that in turn determine chemical properties of a substance e. None of these statements is true

E. none of these are correct

68. The planet Jupiter is about 300 times as massive as Earth, yet on its surface you would weigh only about 3 times as much. This is because

Jupiter's radius is 10 times the Earth's radius

10. A Mack truck and a Volkswagen traveling at the same speed have a head-on collision. The vehicle that undergoes the greatest change in velocity will be the

Volkswagon

64. Compared to the recoiling rifle, the bullet fired has

a greater kinetic energy

80. If one proton is removed from an ordinary helium nucleus, the result is

a heavy isotope of hydrogen

2. Consider a man standing behind a car and pushing it without being able to move the car. Which of the following are an action-reaction force pair?

a man pushing the car and the car pushing the man

7. It takes 5 seconds for a stone to fall to the bottom of a mine shaft. How deep is the shaft?

about 125 m

88. Normal atomic matter makes up what percentage of the universe?

about 4%

12. A truck is moving at constant velocity. Inside the storage compartment, a rock is dropped from the midpoint of the ceiling just before the driver slams on the brakes. The rock hits the floor

ahead of the midpoint of the ceiling

60. A simple lever, properly arranged, is capable of multiplying work input

always false

20. Concerning a road trip, the biggest concern while figuring drive time is ______, while driving through a speed trap is ______, while merging onto an expressway is ________, and while driving along a one-way street is _______.

average speed, instantaneous speed, acceleration, velocity

91. When an object is partly or wholly immersed in a liquid, it is buoyed up

by a force equal to the weight of liquid displaced

47. A heavy truck and a light truck roll down a hill. Neglecting friction, at the bottom of the hill, the light truck will have less: a. speed b. acceleration c. momentum d. all of these e. none of these

c. momentum

1. When an object falls through the air, its velocity increases and its acceleration

decreases

79. The pressure in a liquid depends on liquid

depth & density

56. A car travels in a circle with constant speed. The net force on the car is

directed towards the center of the curve

77. About what percentage of the molecules that make up the atmosphere are below an aircraft that flies at an altitude of 6 kilometers? a. 20% b. 30% c. 40% d. 50% e. more than 50%

e. more than 50%

15. When a book weighing 3 N is lying at rest on a table, the support force that the table exerts on the book is due to

electrical forces between atoms in the book and table

99. The chemical properties of matter come mostly from its

electrons

61. If instead one ball popped out with twice the velocity of the two, this would be a violation of conservation of

energy and momentum

81. Two unequal sized buckets are filled to the top with water. One of the buckets has a piece of wood floating in it, making its total weight

equal to the weight of the other bucket

93. If a battleship sinks in a canal lock, the water level in the lock will

fall

5. A large and a small person wish to parachute at equal terminal velocities. The larger person will have to

get a larger parachute

55. If you push an object half as far, while applying twice the force, you do

half as much work

45. A longer cannon barrel is advantageous because it increases

impulse delivered to the ball by allowing the force to be applied for a longer time & the ball's momentum by increasing its velocity

25. According to Newton's law of inertia, the result of walking much of the day is similar to tightening the head of a hammer when its handle hits a solid surface so that we are actually a little bit shorter

in the evening

35. Consider a rotating donut-shaped space habitat where living quarters are on the inside surface farthest from the axis. If the rotational speed of the habitat increases, the apparent weight of people inside

increases

46. When a twirling ice skater brings her arms inward, her rotational speed

increases

18. Newton's first law of motion: every object continues in its state of rest, or of uniform motion in a straight line, unless it is compelled to change that state by forces impressed upon it. This law is also called the law of

inertia

92. Buoyant force is greatest on a submerged: a. 1- cubic centimeter block of lead b. 1- cubic centimeter block of aluminum c. is the same on each

is the same on each

71. The faster a fluid moves, the

less its internal pressure

98. How much gravitational force is there between two 1-kg steel balls placed 1 m apart from each other?

less than 0.0000000001 N

49. A ball is projected 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

less than 100 J

16. A block is dragged in a straight line path across a level surface by a force of 6 N. What's the force of friction between the block and the surface if the block is speeding up?

less than 6 N

57. A light truck and a heavy truck move with the same momentum. More work is required to stop the

light truck

65. The Burj Khalifa is the tallest freestanding structure in the world. Construction of this building tended to make the length of the day

longer

11. In class, a wooden block was suspended from above by a string. A second sting attached to the bottom of the block hung below. When the lower string was pulled quickly, the lower string broke. This illustrated the block's

mass

48. Stand a meter stick on its end and let go and it rotates to the floor. If you attach a heavy weight to its upper end and repeat, the falling time will be

more

76. According to Newton, decreasing the distance between two interacting objects by half

multiplies by 4 the gravitational force between them

4. A horse exerts 500 N of force on a heavy wagon. The wagon pulls back on the horse with an equal force. The wagon still accelerates because

nevertheless there is still an unbalanced force on the wagon

82. Atoms heavier than hydrogen were made by

nuclear fusion

26. The maximum acceleration of a car while towing a second car twice its mass, compared to its acceleration with no car in tow, is

one third

39. The bead has maximum speed at point

point f, the bottom of the wire

33. In class, we had a tug-of-war between 10 women and 10 men. The men competed in their socks while the women kept their shoes on. The women are sometimes able to pull the men to their side. This happens because the women

push harder on the floor than the men do

44. Your pet hamster sits on a spinning record player. If the angular speed of the record player doubles and he moves to a point half as far from the center, then his linear speed

remains the same

17. According to Galileo, the natural tendency of an object is to

resist the change in motion

50. A ring, a disk, and a solid sphere begin rolling down a hill together. The one to reach the bottom last is the

ring

37. Two people are balanced on a see-saw. If one person leans toward the center of the see-saw, that person's end of the see-saw will

rise

42. A hula hoop has more angular momentum when it is

rolling down a hill with an angular speed of 30 RPM

86. Which of the following substances has a crystalline structure?

silver

32. Two factors that greatly affect air resistance on falling objects are the

size and speed of the object

8. A ball is tossed vertically upward. At its highest point

speed equals zero and velocity equals zero

90. The tides that occur when the sun, earth, and moon are aligned during a full or new moon are

spring tides that are greater than average

28. An object is propelled along a straight-line path by a force. If the net force were halved and the object's mass were halved, the object's acceleration would

stay the same

30. What precisely does a bathroom scale measure?

support force

85. When a load is placed on a horizontal cantilever beam supported at only one end, the top part of the beam undergoes

tension

40. The center of mass of a human body is located at point

that changes as a person bends over

36. Which has greater kinetic energy, a car traveling at 30 km/hr or a car of half the mass traveling at 60 km/hr?

the 60 km/hr car

94. Which produces a greater tidal effect in your body, the moon, the sun, or a 1-kg melon held above your head?

the melon

31. A rock weighs 30 N on earth. A second rock weighs 30 N on the moon. Which of the two rocks has the smaller mass?

the one on Earth

24. What reaction force propels a rocket?

the push of the ejected exhaust gas on the rocket

9. A worker with a mass of 100 kg stands on a 60 kg platform suspended at rest by two ropes. The tension in the first rope is measured to be 900 N. What's the tension in the second rope?

700 N

89. Airplane flight best illustrates

Bernoulli's principle

100. Sound waves cannot travel in

a vacuum

78. In class, I crushed a soda can with

about 3000 N from air pressure

95. As a helium-filled balloon rises in the air, it becomes

bigger

Liquids

take the shape of their container

13. Which of the following statements reflect Aristotle's views of motion?

the sun circles the Earth, an object in its proper place will not move unless acted on by a force, and heavier objects fall faster

75. There are about as many atoms of air in our lungs at any moment as there are breaths of air in the atmosphere of

the whole world

41. If an object is raised twice as high, its potential energy will be

twice as much

69. Tidal forces in general are the result of

unequal forces acting on different parts of the body

96. The reason that buoyant force acts upward on a submerged object is that

upward pressure against the bottom is greater than downward pressure against the top of the submerged object

87. Passengers in a high-flying jumbo jet feel their normal weight in flight, while passengers in the orbiting space shuttle do not. This is because passengers in the space shuttle are

without support forces

34. You cannot touch your toes while standing up against a wall because

your center of gravity will not remain above your feet

14. An object is in mechanical equilibrium if the net force on it is

zero

21. If two 5 pound forces pull on an object in opposite directions, the net force is

0 pounds

6. A falling skydiver of mass 100 kg experiences 70 N air resistance. The acceleration of the skydiver

0.3 kg

38. A 1-kg glider and a 3-kg glider both slide toward each other at 2 m/s on an air track. They collide and stick. The combined mass moves at

1 m/s

54. A rifle of mass 2 kg is suspended by strings. The rifle fires a bullet of mass 1/100 kg at a speed of 200 m/s. The recoil velocity of the rifle is about

1 m/s

63. Two billiard balls of the same mass roll straight toward each other. The first has a velocity of +5 m/s and the second has a velocity of -3 m/s. After colliding, the first ball has a velocity of

- 3 m/s

59. Two 1 kg billiard balls roll toward each other, each moving with speed 10 m/s. What's the combined momentum of the two balls?

0 kg m/s

74. An unstretched hanging spring is 20 cm long. Suspending four 100-N weights from it makes its length 40 cm. Adding two more 100-N weights will make the spring's length

50 cm

23. A person is attracted toward the center of the Earth by a 500-N gravitational force. The Earth is attracted toward the person with a force of

500 N

52. An object held 6 m above the ground has 360 J of potential energy with respect to the ground. What's the object's mass?

6 kg

3. You run 12 miles at 12 mi/hr, but then you get tired and walk 12 miles back at 4 mi/hr. What's your average speed for the entire trip?

6 mi/hr