# Shared Flashcard Set

## Details

Orbital Gravity, Force, Work (General Questinos)
Chapters 5, 6, 7 Physics for Scientists and Engineers
94
Physics
11/03/2013

Term
 Can work be done on a system if there is no motion? A) Yes, if an outside force is provided. B) Yes, since motion is only relative. C) No, since a system which is not moving has no energy. D) No, because of the way work is defined.
Definition
 D) No, because of the way work is defined.
Term
 If you push twice as hard against a stationary brick wall, the amount of work you do A) doubles. B) is cut in half. C) remains constant but non-zero. D) remains constant at zero.
Definition
 D) remains constant at zero.
Term
 A 50-N object was lifted 2.0 m vertically and is being held there.  How much work is being done in holding the box in this position? A) more than 100 J B) 100 J C) less than 100 J, but more than 0 J D) 0 J
Definition
 D) 0 J
Term
 If you walk 5.0 m horizontally forward at a constant velocity carrying a 10-N object, the amount of work you do is   A) more than 50 J. B) equal to 50 J. C) less than 50 J, but more than 0 J. D) zero.
Definition
 D) zero.
Term
 Does the centripetal force acting on an object do work on the object? A) Yes, since a force acts and the object moves, and work is force times distance. B) Yes, since it takes energy to turn an object. C) No, because the object has constant speed. D) No, because the force and the displacement of the object are perpendicular.
Definition
 D) No, because the force and the displacement of the object are perpendicular.
Term
 You throw a ball straight up.  Compare the sign of the work done by gravity while the ball goes up with the sign of the work done by gravity while it goes down. A) Work is + on the way up and + on the way down. B) Work is + on the way up and - on the way down. C) Work is - on the way up and + on the way down. D) Work is - on the way up and - on the way down.
Definition
 C) Work is - on the way up and + on the way down.
Term
 The area under the curve, on a Force versus position (F vs. x) graph, represents A) work. B) kinetic energy. C) power. D) potential energy.
Definition
 A) work.
Term
 The quantity 1/2 mv2 is A) the kinetic energy of the object. B) the potential energy of the object. C) the work done on the object by the force. D) the power supplied to the object by the force.
Definition
 A) the kinetic energy of the object.
Term
 If the net work done on an object is positive, then the object's kinetic energy A) decreases. B) remains the same. C) increases. D) is zero.
Definition
 C) increases.
Term
 If the net work done on an object is negative, then the object's kinetic energy A) decreases. B) remains the same. C) increases. D) is zero.
Definition
 A) decreases.
Term
 If the net work done on an object is zero, then the object's kinetic energy   A) decreases. B) remains the same. C) increases. D) is zero.
Definition
 B) remains the same.
Term
 An object hits a wall and bounces back with half of its original speed.  What is the ratio of the final kinetic energy to the initial kinetic energy?   A) 1/2 B) 1/4 C) 2 D) 4
Definition
 B) 1/4
Term
 You slam on the brakes of your car in a panic, and skid a certain distance on a straight, level road.  If you had been traveling twice as fast, what distance would the car have skidded, under the same conditions? A) It would have skidded 4 times farther. B) It would have skidded twice as far. C) It would have skidded 1.4 times farther. D) It is impossible to tell from the information given.
Definition
 A) It would have skidded 4 times farther.
Term
 A planet of constant mass orbits the Sun in an elliptical orbit.  Neglecting any friction effects, what happens to the planet's kinetic energy?   A) It remains constant. B) It increases continually. C) It decreases continually. D) It increases when the planet approaches the Sun, and decreases when it moves farther away.
Definition
 D) It increases when the planet approaches the Sun, and decreases when it moves farther away.
Term
 The quantity mgy is A) the kinetic energy of the object. B) the gravitational potential energy of the object. C) the work done on the object by the force. D) the power supplied to the object by the force.
Definition
 B) the gravitational potential energy of the object.
Term
 The quantity 1/2 kx^2 is A) the kinetic energy of the object. B) the elastic potential energy of the object. C) the work done on the object by the force. D) the power supplied to the object by the force.
Definition
 B) the elastic potential energy of the object.
Term
 An acorn falls from a tree.  Compare its kinetic energy K, to its potential energy U. A) K increases and U decreases. B) K decreases and U decreases. C) K increases and U increases. D) K decreases and U increases.
Definition
 A) K increases and U decreases.
Term
 A ball falls from the top of a building, through the air (air friction is not present), to the ground below.  How does the kinetic energy (K) just before striking the ground compare to the potential energy (U) at the top of the building? A) K is equal to U. B) K is greater than U. C) K is less than U. D) It is impossible to tell.
Definition
 A) K is equal to U.
Term
 A ball falls from the top of a building, through the air (air friction is present), to the ground below.  How does the kinetic energy (K) just before striking the ground compare to the potential energy (U) at the top of the building? A) K is equal to U. B) K is greater than U. C) K is less than U. D) It is impossible to tell.
Definition
 C) K is less than U.
Term
 A 500-kg elevator is pulled upward with a constant force of 5500 N for a distance of 50.0 m.  What is the work done by the 5500 N force?
Definition
 2.75 × 105 J  (W=Fd cosθ=F.d)
Term
 A 500-kg elevator is pulled upward with a constant force of 5500 N for a distance of 50.0 m.  What is the work done by the weight of the elevator?
Definition
 -2.45 × 105 J (W=F.d=mgh)
Term
 4.00-kg box of fruit slides 8.0 m down a ramp, inclined at 30.0° from the horizontal.  If the box slides at a constant velocity of 5.00 m/s, what is the work done by the weight of the box?
Definition
 157 J  (W =F.d,  F= Fx= mgsinθ,  d=8)             ) or (W=Fd cosθ,  F=mg,  θ=90-30,  d=8)
Term
 A horizontal force of 200 N is applied to move a 55-kg cart (initially at rest) across a 10 m level surface. What is the final kinetic energy of the cart?
Definition
 2.0 × 103 J (ΣW=ΔKE= F.d)
Term
 A horizontal force of 200 N is applied to move a 55-kg cart (initially at rest) across a 10 m level surface.  What is the final speed of the cart?
Definition
 8.5 m/s (ΣW=ΔKE= F.d=½mv2)
Term
 A spring-driven dart gun propels a 10-g dart.  It is cocked by exerting a force of 20 N over a distance of 5.0 cm.  With what speed will the dart leave the gun, assuming the spring has negligible mass?
Definition
 14 m/s  (ΣW=ΔKE= F.d=½mv2) (20N constant force NOT dependant on displacement of spring)  (½kx2 assumes force varies with distance)
Term
 An arrow of mass 20 g is shot horizontally into a bale of hay, striking the hay with a velocity of 60 m/s.  It penetrates a depth of 20 cm before stopping.  What is the average stopping force acting on the arrow?
Definition
 180 N (F.d=½mv2)  (ΣW=ΔKE)
Term
 A 400-N box is pushed up an inclined plane.  The plane is 4.0 m long and rises 2.0 m.  If the plane is frictionless, how much work was done by the push?
Definition
 800 J  (mgh) (ΣW =GPE)
Term
 A spring is characterized by a spring constant of 60 N/m.  How much potential energy does it store, when stretched by 1.0 cm?
Definition
 3.0 × 10-3 J (½kx2 =EPE)
Term
 A 60-kg skier starts from rest from the top of a 50-m high slope.  What is the speed of the slier on reaching the bottom of the slope? (Neglect friction.)
Definition
 31 m/s (½mv2=mgh) (ΔKE=GPE)
Term
 A 1500-kg car moving at 25 m/s hits an initially uncompressed horizontal spring with spring constant of 2.0 × 106 N/m.  What is the maximum compression of the spring? (Neglect the mass of the spring.)
Definition
 0.68 m   (½mv2 =½kx2   ΔKE =EPE)
Term
 A 60-kg skier starts from rest from the top of a 50-m high slope.  If the work done by friction is -6.0 × 103 J, what is the speed of the skier on reaching the bottom of the slope?
Definition
 28 m/s (ΣW=ΔKE)    (ΣW=mgh-Wf= ½mv2)
Term
 At what rate is a 60.0-kg boy using energy when he runs up a flight of stairs 10.0-m high, in 8.00 s?
Definition
 735 W (P=W/t=mgh/t)
Term
 A 10-N force is needed to move an object with a constant velocity of 5.0 m/s.  What power must be delivered to the object by the force?
Definition
 50 WP=W/t=Fv
Term
 A 1500-kg car accelerates from 0 to 25 m/s in 7.0 s.  What is the average power delivered by the engine? (1 hp = 746 W)
Definition
 90 hp (P=W/t) (ΣW=ΔKE½mv2)
Term
 According to Kepler's laws, the paths of planets about the sun are   A) circles. B) straight lines. C) ellipses. D) parabolas. E) none of these.
Definition
 C) ellipses.
Term
 Newton discovered     A) gravity. B) that gravity is universal. C) neither.
Definition
 B) that gravity is universal.
Term
 According to Newton, the greater the masses of interacting objects, the A) greater the gravitational force between them. B) less the gravitational force between them. C) greater the force between them by the square of the masses.
Definition
 A) greater the gravitational force between them.
Term
 According to Newton, doubling the distance between two interacting objects A) multiplies by 2 the gravitational force between them. B) multiplies by 4 the gravitational force between them. C) divides by 4 the gravitational force between them. D) divides by 2 the gravitational force between them.
Definition
 C) divides by 4 the gravitational force between them.
Term
 What is the force of gravity on a 500-newton woman standing on the Earth's surface? A) 50 N B) 250 N C) 500 N D) 509.8 N.
Definition
 C) 500 N
Term
 If the mass of the Earth somehow increased with no change in radius, your weight would A) decrease. B)  increase also. C)  stay the same.
Definition
 B)  increase also.
Term
 Inside a freely-falling elevator, there would be no A) apparent weight for you. B)  gravitational force on you. C) both of these. D)  none of these.
Definition
 A) apparent weight for you.
Term
 A supplier wants to make a profit by buying metal by weight at one altitude and selling it at the same price per pound at another altitude.  The supplier should A) buy at a low altitude and sell at a high altitude. B) disregard altitude because it makes no difference. C) buy at a high altitude and sell at a low altitude.
Definition
 C) buy at a high altitude and sell at a low altitude.
Term
 If the sun somehow became twice as massive, your weight as normally measured here on earth would   A) not change. B)  double. C)  quadruple.
Definition
 A) not change.
Term
 How far must one travel to get away from the Earth's gravitational field?   A) to a region beyond the solar system B) to a region above the Earth's atmosphere C) to a region well beyond the moon D) ...forget it; you can't travel far enough.
Definition
 D) ...forget it; you can't travel far enough.
Term
 When a star collapses to form a black hole, its mass   A) decreases. B)  increases. C)  remains the same.
Definition
 C)  remains the same.
Term
 The Earth is currently accelerating toward the sun (centripetal acceleration). If the sun collapsed into a black hole, this acceleration would   A) stay the same. B)  cease to exist. C)  increase. D)  decrease.
Definition
 A) stay the same.
Term
 If the sun collapsed to a black hole, the Earth's gravitational attraction to it would be   A) more. B)  the same. C)  less.
Definition
 B)  the same.
Term
 The factor most directly responsible for making a black hole invisible is its   A) size. B) color. C) surface escape velocity. D) mass. E) none of these.
Definition
 C) surface escape velocity.
Term
 The reason the moon does not crash into the Earth is that the   A) gravitational pull of other planets keeps the moon up. B) moon has a sufficient tangential speed. C) moon has less mass than the Earth. D) Earth's gravitational field is weak at the moon. E) none of these.
Definition
 B) moon has a sufficient tangential speed.
Term
 Inside a freely-falling runaway elevator, your     A) acceleration is zero. B) gravitational interaction with the Earth is zero. C) apparent weight is zero. D) all of these. E) none of these.
Definition
 C) apparent weight is zero.
Term
 If you drop a stone into a hole drilled all the way to the other side of the Earth (neglect the molten core), the stone will   A) slow down until it reaches the center. B) speed up until it reaches the other side of the Earth. C) come to an abrupt stop at the center of the Earth. D) speed up until it gets to the center of the Earth.
Definition
 D) speed up until it gets to the center of the Earth.
Term
 Horses that move with the fastest linear speed on a merry-go-round are locatedA) near the center.B) anywhere because they all move at the same speed.C) near the outside.
Definition
 C) near the outside.
Term
 Horses that move with the fastest linear speed on a merry-go-round are located A) near the center. B) anywhere because they all move at the same speed. C) near the outside.
Definition
 C) near the outside.
Term
 If you use large-diameter tires on your car, for a given RPM your linear speed will be A) less. B)  more. C)  no different.
Definition
 B)  more.
Term
 If a record player's rotational speed is doubled, then the linear speed of a pet hamster sitting on the edge of the record will A) halve. B)  double. C)  remain the same.
Definition
 B)  double.
Term
 An upright broom is easier to balance when the heavier end is A) highest, farthest from your hand. B) nearest your hand. C) same either way.
Definition
 A) highest, farthest from your hand.
Term
 An industrial flywheel has a greater rotational inertia when most of its mass is A) nearest the rim. B) uniformly spread out as in a disk. C) nearest the axis.
Definition
 A) nearest the rim.
Term
 A coin and a ring roll down an incline starting at the same time.  The one to reach the bottom first will be the A) ring. B) coin. C) both reach the bottom at the same time.
Definition
 B) coin.
Term
 A torque acting on an object tends to produce A) rotation. B) velocity. C) equilibrium. D) a center of gravity. E) linear motion.
Definition
 A) rotation.
Term
 On a balanced see saw, a boy three times as heavy as his partner sits A) more than 1/3 the distance from the fulcrum. B) less than 1/3 the distance from the fulcrum. C) 1/3 the distance from the fulcrum.
Definition
 C) 1/3 the distance from the fulcrum.
Term
 Put a pipe over the end of a wrench when trying to turn a stubborn nut on a bolt, to effectively make the wrench handle twice as long, you'll multiply the torque by A) two. B)  four. C)  eight.
Definition
 A) two.
Term
 Toss a baseball bat into the air and it wobbles about its A) geometrical center. B)  heavier end. C)  center of mass.
Definition
 C)  center of mass.
Term
 The famous Leaning Tower of Pisa doesn't topple over because its center of gravity is A) above a place of support. B) relatively low for such a tall building. C) in the same place as its center of mass. D) stabilized by its structure. E) displaced from its center.
Definition
 A) above a place of support.
Term
 When a twirling ice skater brings her arms inward, her rotational speed A) decreases. B)  remains the same. C)  increases.
Definition
 C)  increases.
Term
 A tightrope walker more easily balances on a tightwire if his pole A) is short but heavy. B)  droops. C)  is held high.
Definition
 B)  droops.
Term
 A ring, a disk, and a solid sphere begin rolling down a hill together.  The one to reach the bottom first is the A) disk. B) ring. C) sphere. D) they all reach the bottom at the same time. E) not enough information is given.
Definition
 C) sphere.
Term
 Suppose you put very large-diameter tires on your car. Then, your speedometer will show a speed that is A) lower than it is actually. B)  higher than it is actually.
Definition
 A) lower than it is actually.
Term
 If you push an object twice as far while applying the same force you do A) the same amount of work. B) twice as much work. C) four times as much work.
Definition
 B) twice as much work.
Term
 A job is done slowly, while an identical job is done quickly. Both jobs require the same amount of work, but different amounts of A) energy. B)  power. C)  both of these. D)  none of these.
Definition
 B)  power.
Term
 Exert 1 N for a distance of 1 m in 1 s and you deliver a power of A) 1 W. B) 2 W. C) 1/3 W. D) 3 W. E) none of these.
Definition
 A) 1 W.
Term
 When an object is raised above the ground it gains a certain amount of potential energy.  If the same object is raised twice as high it gains A) four times as much potential energy. B) twice as much potential energy. C) neither of these.
Definition
 B) twice as much potential energy.
Term
 An object that has kinetic energy must be A) falling. B) at rest. C) at an elevated position. D) moving. E) none of these.
Definition
 D) moving.
Term
 Bullets are fired from an airplane in the forward direction of motion.  The momentum of the airplane will be A) increased. B)  decreased. C)  unchanged.
Definition
 B)  decreased.
Term
 A bow is drawn so that it has 40 J of potential energy. When fired, the arrow will ideally A) 40 J. B)  more than 40 J. C)  less than 40 J. have a kinetic energy of
Definition
 A) 40
Term
 When a car is braked to a stop, its kinetic energy is transformed to A) energy of motion. B) potential energy. C) heat. D) stopping energy. E) energy of rest.
Definition
 C) heat.
Term
 A car moves 4 times as fast as another identical car.  Compared to the slower car, the faster car has A) 4 times the KE. B)  8 times the KE. C) 12 times the KE. D)  16 times the KE.
Definition
 D)  16 times the KE.
Term
 A woman lifts a box from the floor.  She then moves with constant speed to the other side of the room, where she puts the box down.  How much work does she do on the box while walking across the floor at constant speed? A) zero J   B) more than zero J   C) more information needed to determine
Definition
 A) zero J
Term
 According to Kepler's laws, the paths of planets about the Sun are
Definition
 ellipses
Term
 According to Newton, the greater the masses of interacting objects, the
Definition
 greater the force of gravity, by the product of the masses F = G M m / d^2
Term
 According to Newton, the greater the distance between masses of interacting objects, the
Definition
 less the force of gravity, inversely as the square of the distance F = G M m / d^2
Term
 If the mass of the earth somehow increased with no change in radius, your weight would
Definition
 increase F = G M m / d^2
Term
 If the radius of Earth somehow decreased with no change in mass, your weight would
Definition
 increase F = G M m / d2
Term
 If Earth's mass decreased to one-half its original mass with no change in radius, then your weight would
Definition
 decrease to one-half its original value F = G M m / d2
Term
 The force of gravity acting on the Space Shuttle in orbit is nearly
Definition
 equal to the weight of the Space Shuttle at Earth's surface F = G M m / d2 In a low-Earth orbit, the Space Shuttle's distance from the center of Earth is nearly the same as it was at Earth's surface.
Term
 A woman who normally weighs 400 N stands on top of a very tall ladder so she is one earth radius above the earth's surface. How much would she weigh there?
Definition
 100 N F = G M m / d2 If d is made twice as large, then d2 will be four times as large. Since we are dividing by d2, this means the Force -- her weight -- will be only one-fourth as much.
Term
 The force of gravity acts on all apples on an apple tree. Some apples are twice as far from the ground as others. These twice- as-high apples, for the same mass, have practically
Definition
 the same weight F = G M m / d2 Being twice as far above the ground has hardly any effect on d, the distance from the center of Earth to the apple.
Term
 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
Definition