Physics 100-Study guide for Exam 2-Chapters 5, 7, 8
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The action is: Earth pulls on Moon. What is the reaction? a) Moon pulls on Sun. b) Moon pulls on Earth. c) Earth pushes on Moon. d) Moon pushes on Earth.
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b) Moon pulls on Earth
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Which force is greater, the Earth's pull on the Moon, or the Moon's pull on the Earth? a) Moon's pull b) Both pulls are the same. c) Earth's pull
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b) both pulls are the same
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If the cannon's recoil is the result of an equal and opposite reaction, why is the cannon's acceleration lower than the shell's acceleration? a) Not as much force is applied to it. b) The cannon's acceleration is not lower than the shell's acceleration; it has the same acceleration as the shell. c) The cannon has more mass than the shell.
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c) the cannon has more mass than the shell
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Since movement of an object or system requires that a net force be applied to it, how can this occur if all action forces have opposite and equal reaction forces? a) The action force doesn't act on the same object as the reaction force. b) Sometimes there are singular (unpaired) forces acting on an object. c) Newton was never able to explain this.
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a) the action force doesn't act on the same object as the reaction force
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The horse is pulling a cart. What allows the horse to accelerate forward even though the cart is pulling back on the horse? a) Friction from the ground on the horse is stronger than the sideways force the horse is exerting on the ground. b) The horse is pulling on the cart with a stronger force than the cart is pulling back on the horse. c) The force of friction the ground exerts on the horse is larger than the force the cart is pulling back on the horse.
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c) The force of friction the ground exerts on the horse is larger than the force the cart is pulling back on the horse.
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Which of the following is NOT a statement or consequence of Newton's third law? a) There can never be only one force acting on an object. b) No force can exist on its own. c) All forces come in pairs. d) Every force has an opposite and equal reaction.
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a) There can never be only one force acting on an object.
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Which force diagram could be representing a reaction pair? a) two arrows of equal length back to back pointing in opposite directions b) two arrows pointing in opposite directions: one straight and one at a downward angle c) two arrows of unequal length back to back pointing in opposite directions
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a) two arrows of equal length back to back pointing in opposite directions
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A heavy crate is attached to the wall by a light rope, as shown in the figure. Another rope hangs off the opposite edge of the box. If you slowly increase the force on the free rope by pulling on it in a horizontal direction, which rope will break? Ignore friction and the mass of the ropes. a) The rope attached to the wall will break. b) The rope that you are pulling on will break. c) Both ropes are equally likely to break.
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c) Both ropes are equally likely to break.
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Replace the original 56-g magnet with a more powerful magnet of the same mass. As you know from experience, the more powerful a magnet is, the more strongly it attracts or repels other magnets or magnetic objects. You have also probably noticed that magnetic forces fall off sharply with distance—two magnets that interact strongly across a distance of millimeters interact more weakly at a distance of a centimeter. (In fact, the strength of the force falls off with the square of the distance.) With the magnet hovering above the base, what will the scale read? The scale has been zeroed (tared) to subtract the weight of the base. a) More than 56 g b) -56 g c) 0 g d) Less than 56 g but greater than 0 g e) 56 g
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e) 56 g Expanation: In equilibrium, the base must push up on the magnet with a force equal to the weight of the magnet, and the magnet will exert an equal-but-opposite force on the base. The reading on the scale will not change.
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How does the force on the rifle compare with the force on the bullet, and why? a) The force on the rifle is greater than the force on the bullet because the mass of the rifle is greater. b) The magnitude of the force of the rifle is equal to the magnitude of force on the bullet and the forces are in the opposite direction, because for every action there is an equal and opposite reaction. c) The force on the rifle is less than the force on the bullet because the mass of the rifle is greater. d) The magnitude of the force of the rifle is equal to the magnitude of force on the bullet and both forces are in the same direction, because for every action there is an equal reaction.
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b) The magnitude of the force of the rifle is equal to the magnitude of force on the bullet and the forces are in the opposite direction, because for every action there is an equal and opposite reaction.
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How does the magnitude of acceleration of the rifle compare with the magnitude of acceleration of the bullet, and why? a) The magnitude of acceleration of the rifle is equal to the magnitude of acceleration of the bullet because they experience the same magnitude of force. b) The magnitude of acceleration of the rifle is greater than the magnitude of acceleration of the bullet. Even though they experience the same magnitude of force, the mass of the rifle is greater, and so the rifle will experience a greater acceleration than the bullet. c) The acceleration of the rifle is smaller than the acceleration of the bullet. They experience the same magnitude of force, but the mass of the rifle is greater, and so the rifle will experience a smaller acceleration than the bullet.
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c) The acceleration of the rifle is smaller than the acceleration of the bullet. They experience the same magnitude of force, but the mass of the rifle is greater, and so the rifle will experience a smaller acceleration than the bullet.
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How does the distance traveled by the bullet compare with the distance traveled by the rifle in the same time, and why? a) The bullet will travel the same distance as the rifle because they have equal magnitudes of acceleration. b) The rifle will travel farther than the bullet because it has a greater magnitude of acceleration. c) The bullet will travel farther than the rifle because it has a greater magnitude of acceleration.
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c) The bullet will travel farther than the rifle because it has a greater magnitude of acceleration.
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For an action force, there must be a reaction force that a) is slightly smaller in magnitude than the action force. b) is exactly equal in magnitude. c) is slightly larger in amplitude than the action force. d) always acts in the same direction.
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b) is exactly equal in magnitude
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A player hits a ball with a bat. The action force is the impact of the bat against the ball. The reaction to this force is the a) force that the ball exerts on the bat. b) grip of the player's hand against the ball. c) weight of the ball. d) air resistance on the ball. e) weight of the bat.
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a) force that the ball exerts on the bat
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Arnold Strongman and Suzie Small each pull very hard on opposite ends of a massless rope in a tug-of-war. The greater force on the rope is exerted by a) Suzie, surprisingly. b) Arnold, of course. c) both the same, interestingly enough.
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c) both the same, interestingly enough
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A boxer cannot exert much force on a piece of tissue paper suspended in air because _______. a) the tissue paper has too little mass to exert much force on the boxer's fist b) the tissue lacks enough strength c) the time of the interaction is too brief d) there is little follow-through with the punch
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a) the tissue paper has too little mass to exert much force on the boxer's fist
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The force that propels a rocket is the force provided by _______. a) decreased mass b) ejected fuel c) energetic reactions as the fuel is burned d) the expelled gas pushing on the rocket
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d) the expelled gas pushing on the rocket
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In the apple-pulling-the-orange sequence in this chapter, what is the force that accelerates the system across the floor? a) Internal forces b) The resistance to motion by the orange c) The backward pull by the orange d) Friction between the apple and the floor
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d) friction between the apple and the floor
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The team that will win in a tug-of-war is the team that _______. a) yanks the rope b) has the greater self confidence. c) pulls with the greater force d) pushes harder on the floor while holding the rope
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d) pushes harder on the floor while holding the rope
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When hitting a tennis ball with your racquet, the force on the ball has the same magnitude as the force on the _______. a) racquet, and in the same direction b) hand that holds the racquet c) racquet d) player
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c) racquet
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A Volkswagen bug and a Volvo truck have a head-on collision. Which statement is true? a) Both forces are identical. b) The greater force acts on the Volkswagen bug. c) The magnitudes of both forces are the same. d) The greater force acts on the Volvo truck.
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c) the magnitudes of both forces are the same
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When you push against a wall, what pushes back? a) The wall b) Your fingers c) Your hand d) Nothing
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a) the wall
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As a ball falls, the action force is the pull of Earth on the ball. The reaction force is the a) air resistance acting against the ball. b) acceleration of the ball. c) pull of the ball's mass on the Earth. d) none of these
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c) pull of the ball's mass on the Earth
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The attraction of a person's body toward Earth is called weight. The reaction to this force is a) the Earth's surface pushing against the person's body. b) the person's body pushing against Earth's surface. c) the person's body pulling on the Earth. d) none of these
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c) the person's body pulling on the Earth
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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 a) Volkswagen. b) Mack truck. c) same for both.
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a) Volkswagen
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How many forces are required for an interaction? a) One force, an action, is needed for an interaction. b) Two forces, an action and a reaction, are needed for an interaction. c) Two forces, a contact force and a friction force, are needed for an interaction. d) One force, a reaction, is needed for an interaction.
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b) Two forces, an action and a reaction, are needed for an interaction.
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To produce a net force on a system, must there be an externally applied net force? a) No, an internal net force is sufficient. b) No. To accelerate, the internal action forces must not equal the internal reaction forces. c) Yes. To accelerate, the internal reaction forces must be zero. d) Yes, there must be an external net force on the system.
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c) Yes. To accelerate, the internal reaction forces must be zero.
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Can you physically touch a person without that person touching you with the same amount of force? a) Yes, when you touch a person, they touch you back with a force that is slightly less due to friction. b) No, when you touch a person, they must touch you with an equal and opposite force. c) Yes, you can touch a person while they choose to not touch you back. d) Yes, when a heavier person touches a lighter person, the lighter person touches back with less force.
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b) No, when you touch a person, they must touch you with an equal and opposite force.
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Fill in the blanks: Newton's first law is often called the law of ____; Newton's second law is the law of ____; and Newton's third law is the law of ____. a) Inertia, net force, friction b) Inertia, acceleration, action -reaction c) Acceleration, inertia, action -reaction d) Action, inertia, force
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b) inertia, acceleration, action-reaction
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A piece of rope is pulled by two people in a tug-of-war. Each exerts a 400-N force. What is the tension in the rope? a) 600 N b) zero c) 800 N d) 400 N e) none of the above
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d) 400 N
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When you walk, you push on the floor to the left and the floor a) pushes you to the right. b) also pushes on you to the left. c) can only wish it could push on you. d) both of these simultaneously. e) none of the above ******************
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a) pushes you to the right *******************
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What happens the first time Dr. Hewitt lifts the bowling ball near his teeth and lets go? a) The ball leaves Dr. Hewitt and returns to him, stopping short of the point where it was released. b) The ball leaves Dr. Hewitt and returns to him, going past the point where it was released. c) The ball returns to Dr. Hewitt, stopping almost exactly at the point where it was released.
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c) The ball returns to Dr. Hewitt, stopping almost exactly at the point where it was released.
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Why does the bowling ball behave the way it does the first time Dr. Hewitt lifts the bowling ball near his teeth and lets go? a) All of the initial energy of the ball was lost when the ball was released. b) All of the initial energy of the ball was converted completely back to potential energy when the ball returned. c) Some of the initial energy of the ball was lost, and it had less energy than it had at the beginning.
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b) All of the initial energy of the ball was converted completely back to potential energy when the ball returned.
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What happens the second time Dr. Hewitt lifts the bowling ball near his teeth and gives it a push? a) The ball leaves Dr. Hewitt and returns to him, stopping short of the point where it was released. b) The ball leaves Dr. Hewitt and returns to him, going past the point where it was released. c) The ball returns to Dr. Hewitt, stopping almost exactly at the point where it was released.
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b) The ball leaves Dr. Hewitt and returns to him, going past the point where it was released.
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Why does the bowling ball behave as it does when Dr. Hewitt lifts it and gives it a push? a) The extra energy from the push is converted into kinetic energy, which is then converted into more potential energy at the end of the motion than the ball had when it was released. b) The ball gains potential energy after it is released. c) The ball's initial energy is lost.
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a) The extra energy from the push is converted into kinetic energy, which is then converted into more potential energy at the end of the motion than the ball had when it was released.
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Calculate the work done when a 12-N force pushes a cart 3.2 m . Express your answer to two significant figures and include the appropriate units.
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W=Fd (Work=force x distance) W= 12 N x 3.2 m W=38 J
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How many joules of potential energy does a 1.0-kg book gain when it is elevated 3.2 m ? Express your answer to two significant figures and include the appropriate units.
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PE=mgh (Gravitational potential energy=weight x height) ΔPE = 1.0 x 3.2 ΔPE = 31 J
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When it is elevated 6.4 m ? Express your answer to two significant figures and include the appropriate units.
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ΔPE = 1.0 x 6.4 ΔPE = 63 J
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Calculate the number of joules of kinetic energy a 1.3-kg book has when tossed at a speed of 1.8 m/s . Express your answer to two significant figures and include the appropriate units.
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KE = 1/2mv2 (Kinetic energy = 1/2 mass × speed2) KE = 1/2(1.3) x 1.8 squared KE = 2.1 J
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The roller coaster ride starts from rest at point A. Rank from greatest to least at each point.
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D B E C A
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The roller coaster ride starts from rest at point A. Rank kinetic energy from greatest to least at each point.
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D B E C A
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The roller coaster ride starts from rest at point A. Rank potential energy from greatest to least at each point.
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A E C B D
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The work that is done when twice the load is lifted twice the distance is _______. a) three times as much b) the same c) four times as much d) twice as much
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c) four times as much
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When one does twice the work in twice the time, the power expended is _______. a) the same b) twice as much c) three times as much d) four times as much
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a) the same
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When you lift twice the load twice as high, in half the time, the increase in potential energy is _______. a) double b) three times as much c) the same d) four times as much
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d) four times as much
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When traveling twice as fast your kinetic energy is increased _______. a) not at all b) by four c) by three d) by two
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b) by four
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Energy cannot be _______. a) destroyed b) transferred c) transformed d) transferred, transformed, or destroyed
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a) destroyed
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In a simple machine, how much work is done when an input of 10 N acts over a distance of 5 m? a) 50 J b) 15 J c) 10 J d) 5 J
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a) W = Fd W = 10 N x 5 m W = 50 J
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If you push an object twice as far while applying the same force, you do a) half as much work. b) twice as much work. c) the same amount of work. d) four times as much work.
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b) twice as much work
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An object lifted 10 meters gains 200 J of potential energy. If the same object is lifted 20 meters, its potential energy gain is a) half as much. b) four times as much. c) twice as much. d) more than four times as much. e) the same.
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c) twice as much
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When properly used, a hydraulic press, like a wheel and axle, is capable of multiplying force input. a) sometimes false b) always true c) sometimes true d) always false
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b) always true
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A car moves 4 times as fast as another identical car. Compared to the slower car, the faster car has a) 12 times the KE. b) 4 times the KE. c) 16 times the KE. d) 8 times the KE.
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c) 16 times the KE
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If you find that twice as much work is needed to perform a task but it takes twice as much time, the amount of power required is a) sixteen times as much. b) four times as much. c) unchanged. d) twice as much.
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c) unchanged
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Do 100 J of work in 50 s and your power output is a) 2 W. b) 1/2 W c) 4 W. d) 50 W. e) 5,000 W.
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a) 2 W
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A bow is drawn so that it has 40 J of potential energy. When fired, the arrow will ideally have a kinetic energy that is a) less than 40 J. b) more than 40 J. c) 40 J. d) impossible to predict without additional information
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c) 40 J
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How much work is done on a satellite in a circular orbit about Earth? a) Zero b) The mass of the satellite times the circumference of the orbit c) The weight of the satellite times the circumference of the orbit d) The gravity force on the satellite times the diameter of the orbit
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a) zero
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Exactly what is it that enables an object to do work? a) Momentum b) Heat c) Energy d) Impulse
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c) energy
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What will the kinetic energy of a pile driver ram be if it starts from rest and undergoes a 10 kJ decrease in potential energy? a) -10 kJ b) 10 kJ c) 5 kJ d) 0 kJ
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b) 10 kJ
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An apple hanging from a limb has potential energy because of its height. If it falls, what becomes of this energy just before it hits the ground? When it hits the ground? a) The energy is potential energy before it hits the ground; it is thermal energy after. b) The energy is kinetic energy before it hits the ground; it is potential energy after. c) The energy is thermal energy before it hits the ground; it is kinetic energy after. d) The energy is kinetic energy before it hits the ground; it is thermal energy after.
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d) the energy is kinetic energy before it hits the ground; it is thermal energy after
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If a machine multiplies force by a factor of 4, what other quantity is diminished, and by how much? a) Distance is diminished to one-half. b) Energy is diminished to one-half. c) Energy is diminished to one-quarter. d) Distance is diminished to one-quarter. ********************************
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d) distance is diminished to one-quarter ***********************************
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Rank the torque needed to keep the stick steady, from largest to smallest.
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B C A
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The torque exerted by a crowbar on an object increases with increased _______. a) force and leverage distance b) force c) rotational inertia d) energy of application
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a) force and leverage distance
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An automobile speedometer is configured to read speed proportional to the rotational speed of its wheels. If larger wheels, such as those of snow tires, are used, will the speedometer reading be high, or low-or no different? a) low b) high c) no different
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a) low
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Can a force produce a torque when there is no lever arm? a) yes b) no
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b) no
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Horses that move with the fastest linear speed on a merry-go-round are located a) near the outside. b) near the center. c) anywhere, because they all move at the same speed.
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a) near the outside
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To turn a stubborn screw, it is best to use a screwdriver that has a a) wide handle. b) smooth handle. c) long handle. d) none of these
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a) wide handle
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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 a) is always zero. b) increases. c) decreases. d) stays the same.
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b) increases
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The tangential speed on the outer edge of a rotating carousel is _______. a) less than toward the center b) greater than toward the center c) the same as toward the center d) four times as great for twice the distance
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b) greater than toward the center
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A torque acting on an object tends to produce a) equilibrium. b) a center of gravity. c) linear motion. d) velocity. e) rotation.
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e) rotation
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What are the units of measurement for tangential speed? For rotational speed? a) RPM for tangential, m/s for rotational b) m/s for both c) RPM for both d) m/s for tangential, RPM for rotational
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d) m/s for tangential, RPM for rotational
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If you hang at rest by your hands from a long vertical rope, where is your center of gravity with respect to the rope? a) At the end of the rope b) Where your hands grab the rope c) Somewhere straight below where your hands grab the rope d) Somewhere straight above where your hands grab the rope
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c) somewhere straight below where your hands grab the rope
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Where is the center of mass of a hollow soccer ball? a) At the top-dead-center of the ball b) In the center of the ball c) At the lowest point of the ball d) Halfway between the center and the lowest point of the ball
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b) in the center of the ball
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When you whirl a can at the end of a string in a circular path, what is the direction of the force you exert on the can? a) Toward the center of the circle b) Tangent to the circle in the direction of motion of the can c) Tangent to the circle and opposite in direction to the motion of the can d) Radially outward from the center of the circle
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a) toward the center of the circle
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If you are not wearing a seat belt in a car that rounds a curve, and you slide across your seat and slam against a car door, what kind of force is responsible for your slide: centripetal, centrifugal, or no force? a) It is centrifugal force as viewed by someone outside the car. b) It is centripetal force, but only as viewed by someone inside the car. c) Centripetal force d) There is no force as viewed by someone outside the car. To them you move in a straight line.
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d) There is no force as viewed by someone outside the car. To them you move in a straight line.
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Dan and Sue cycle at the same speed. The tires on Dan's bike are larger in diameter than those on Sue's bike. Which wheels, if either, have the greater rotational speed? a) Sue's wheels have the greater rotational speed. b) Dan's wheels have the greater rotational speed. c) They have the same rotational speed.
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a) Sue's wheels have the greater rotational speed
