Physics Chapter 4, Chapter 6, Chapter 7
A locomotive is pulling 19 freight cars, each of which is loaded with the same amount of weight. The mass of each freight car (with its load) is 37,000 kg. If the train is accelerating at 0.22 m/s2 on a level track, what is the tension in the coupling between the second and third cars? (The car nearest the locomotive is counted as the first car, and friction is negligible.)
140,000N
A 7.0-kg rock is subject to a variable force given by the equation F(x) = 6.0 N - (2.0 N/m)x + (6.0 N/m2)x2 If the rock initially is at rest at the origin, find its speed when it has moved 9.0 m
20 m/s
A box of mass 50 kg is at rest on a horizontal frictionless surface. A constant horizontal force F then acts on the box and accelerates it to the right. It is observed that it takes the box 6.9 seconds to travel 28 meters. What is the magnitude of the force?
59N
8) When an object is solely under the influence of conservative forces, the sum of its kinetic and potential energies does not change. A) True B) False
A
If a force always acts perpendicular to an object's direction of motion, that force cannot change the object's kinetic energy. A) True B) False
True
A stalled car is being pushed up a hill at constant velocity by three people. The net force on the car is A) zero. B) up the hill and equal to the weight of the car. C) down the hill and equal to the weight of the car. D) up the hill and greater than the weight of the car. E) down the hill and greater than the weight of the car.
A
1) Is it possible for a system to have negative potential energy? A) Yes, as long as the kinetic energy is positive. B) Yes, as long as the total energy is positive. C) Yes, since the choice of the zero of potential energy is arbitrary. D) No, because the kinetic energy of a system must equal its potential energy. E) No, because this would have no physical meaning.
C
A block lies on a horizontal frictionless surface. A horizontal force of 100 N is applied to the block giving rise to an acceleration of 3.0 m/s2. (a) Determine the mass of the block. (b) Calculate the distance the block will travel if the force is applied for 10 s. (c) Calculate the speed of the block after the force has been applied for 10 s.
(a) 33 kg (b) 150 m (c) 30 m/s
Three cars (car F, car G, and car H) are moving with the same velocity when the driver suddenly slams on the brakes, locking the wheels. The most massive car is car F, the least massive is car H, and all three cars have identical tires. (a) Which car travels the longest distance to skid to a stop? A) Car F B) Car G C) Car H D) They all travel the same distance in stopping. (b) For which car does friction do the largest amount of work in stopping the car? A) Car F B) Car G C) Car H D) The amount of work done by friction is the same for all cars
(a) D (b) A
A construction worker pulls a box of tools on a smooth horizontal floor with a force of 100 N in a direction of 37.0° above the horizontal. The mass of the box and the tools is 40.0 kg. (a) Draw a free-body diagram for the box. (b) Calculate the acceleration of the box. (c) How hard does the floor push up on the box?
(a) The box is acted on by the force of gravity which points downward toward the center of the earth. The normal force is directed toward the box perpendicular to the surface of the floor. The pulling force is directed away from the box at an angle 37.0 degrees above the horizontal. (b) 2.00 m/s2 (c) 332 N
A crane lifts a 425 kg steel beam vertically a distance of 117 m. How much work does the crane do on the beam if the beam accelerates upward at 1.8 m/s2? Neglect frictional forces. A) 5.8 × 105 J B) 3.4 × 105 J C) 4.0 × 105 J D) 4.9 × 105 J
A
1) An 8.0-kg block is released from rest, with v1 = 0.00 m/s, on a rough incline, as shown in the figure. The block moves a distance of 1.6-m down the incline, in a time interval of 0.80 s, and acquires a velocity of v2 = 4.0 m/s. How much work does gravity do on the block during this process? A) +81 J B) +100 J C) +120 J D) -81 J E) -100 J
A
2) You do 174 J of work while pulling your sister back on a swing, whose chain is 5.10 m long. You start with the swing hanging vertically and pull it until the chain makes an angle of 32.0° with the vertical with your sister is at rest. What is your sister's mass, assuming negligible friction? A) 22.9 kg B) 19.5 kg C) 26.3 kg D) 28.4 kg
A
3) An athlete stretches a spring an extra 40.0 cm beyond its initial length. How much energy has he transferred to the spring, if the spring constant is 52.9 N/cm? A) 423 J B) 4230 kJ C) 423 kJ D) 4230 J
A
4) A tennis ball bounces on the floor three times. If each time it loses 22.0% of its energy due to heating, how high does it rise after the third bounce, provided we released it 2.3 m from the floor? A) 110 cm B) 11 cm C) 110 mm D) 140 cm
A
9) A ball drops some distance and gains 30 J of kinetic energy. Do NOT ignore air resistance. How much gravitational potential energy did the ball lose? A) more than 30 J B) exactly 30 J C) less than 30 J
A
A 1000 kg car experiences a net force of 9500 N while decelerating from 30.0 m/s to 23.4 m/s. How far does it travel while slowing down? A) 18.5 m B) 17.4 m C) 20.2 m D) 21.9 m
A
A 1000.0 kg car is moving at 15 km/h. If a 2000.0 kg truck has 18 times the kinetic energy of the car, how fast is the truck moving? A) 45 km/h B) 63 km/h C) 54 km/h D) 36 km/h
A
A 50.0-N box is sliding on a rough horizontal floor, and the only horizontal force acting on it is friction. You observe that at one instant the box is sliding to the right at 1.75 m/s and that it stops in 2.25 s with uniform acceleration. What magnitude force does friction exert on this box? A) 3.97 N B) 8.93 N C) 38.9 N D) 50.0 N E) 490 N
A
A ball is thrown upward at an angle with a speed and direction such that it reaches a maximum height of 16.0 m above the point it was released, with no appreciable air resistance. At its maximum height it has a speed of 18.0 m/s. With what speed was the ball released? A) 25.3 m/s B) 22.2 m/s C) 33.0 m/s D) 29.2 m/s E) 36.9 m/s
A
A ball is tossed vertically upward. When it reaches its highest point (before falling back downward) A) the velocity is zero, the acceleration is directed downward, and the force of gravity acting on the ball is directed downward. B) the velocity is zero, the acceleration is zero, and the force of gravity acting on the ball is zero. C) the velocity is zero, the acceleration is zero, and the force of gravity acting on the ball is directed downward. D) the velocity and acceleration reverse direction, but the force of gravity on the ball remains downward. E) the velocity, acceleration, and the force of gravity on the ball all reverse direction.
A
A block is on a frictionless horizontal table, on earth. This block accelerates at 1.9 m/s2 when a 90 N horizontal force is applied to it. The block and table are then set up on the moon where the acceleration due to gravity is 1.62 m/s2. What is the weight of the block on the moon? A) 77 N B) 67 N C) 58 N D) 48 N E) 39 N
A
A block is on a frictionless horizontal table, on earth. This block accelerates at 3.6 m/s2 when a 90 N horizontal force is applied to it. The block and table are then set up on the moon where the acceleration due to gravity is 1.62 m/ s2. A horizontal force of 45 N is applied to the block when it is on the moon. What acceleration does this force impart to the block? A) 1.8 m/s2 B) 1.6 m/s2 C) 2.0 m/s2 D) 2.2 m/s2 E) 2.3 m/s2
A
A car needs to generate 75.0 hp in order to maintain a constant velocity of 27.3 m/s on a flat road. What is the magnitude of the total resistive force acting on the car (due to friction, air resistance, etc.)? (1 hp = 746 W) A) 2.05 × 103 N B) 2.75 N C) 1.03 × 103 N D) 2.87 × 103 N
A
A child pulls on a wagon with a horizontal force of 75 N. If the wagon moves horizontally a total of 42 m in 3.0 min, what is the average power generated by the child? A) 18 W B) 22 W C) 24 W D) 27 W
A
A dog is standing in the bed of a pickup truck. The bed is coated with ice, causing the force of friction between the dog and the truck to be zero. The truck is initially at rest, and then accelerates to the right, moving along a flat road. As seen from a stationary observer (watching the truck move to the right), the dog A) does not move left or right, but the back of the truck moves towards the dog. B) moves to the right, but not as quickly as the truck is moving to the right, causing it to slide towards the back of the truck. C) moves to the right at the same rate as the truck, so it doesn't slide. D) moves to the left, as the truck moves to the right, causing the dog to slide towards the back of the truck.
A
A force = 12 N î - 10 N ĵ acts on an object. How much work does this force do as the object moves from the origin to the point r=13m i + 11m j A) 46 J B) 266 J C) 37 J D) 62 J Answer: A
A
A force F = bx3 acts in the x direction, where the value of b is 3.7 N/m3. How much work is done by this force in moving an object from x = 0.00 m to x = 2.6 m? A) 42 J B) 13 J C) 50 J D) 57 J
A
A person pushes horizontally on a heavy box and slides it across the level floor at constant velocity. The person pushes with a 60.0 N force for the first 6.88 m, at which time he begins to tire. The force he exerts then starts to decrease linearly from 60.0 N to 0.00 N across the remaining 6.88 m. How much total work did the person do on the box? A) 619 J B) 826 J C) 495 J D) 925 J
A
A spring stretches by 21.0 cm when a 135 N object is attached. What is the weight of a fish that would stretch the spring by 31 cm? A) 199 N B) 91.0 N C) 145 N D) 279 N
A
A traveler pulls on a suitcase strap at an angle 36° above the horizontal. If 908 J of work are done by the strap while moving the suitcase a horizontal distance of 15 m, what is the tension in the strap? A) 75 N B) 61 N C) 85 N D) 92 N
A
An 1100-kg car traveling at 27.0 m/s starts to slow down and comes to a complete stop in 578 m. What is the magnitude of the average braking force acting on the car? A) 690 N B) 550 N C) 410 N D) 340 N
A
An airplane flies 120 km at a constant altitude in a direction 30.0° north of east. A wind is blowing that results in a net horizontal force on the plane due to the air of 2.40 kN in a direction 10.0° south of west. How much work is done on the plane by the air? A) -2.71 × 108 J B) -0.985 × 108 J C) -221 × 108 J D) 221 × 108 J E) 0.821 × 108 J
A
An object attached to an ideal massless spring is pulled across a frictionless surface. If the spring constant is 45 N/m and the spring is stretched by 0.88 m when the object is accelerating at 2.0 m/s2, what is the mass of the object? A) 20 kg B) 17 kg C) 22 kg D) 26 kg
A
An object is moving forward with a constant velocity. Which statement about this object MUST be true? A) The net force on the object is zero. B) The net force on the object is in the forward direction. C) No forces are acting on the object. D) The acceleration of the object is in the forward direction.
A
An object is moving to the right, and experiencing a net force that is directed to the right. The magnitude of the force is decreasing with time. The speed of the object is A) increasing. B) decreasing. C) constant in time.
A
Calculate the minimum average power output necessary for a 55.8 kg person to run up a 12.0 m long hillside, which is inclined at 25.0° above the horizontal, in 3.00 s. You can neglect the person's kinetic energy. Express your answer in horsepower. (1 hp = 746 W) A) 1.24 hp B) 2.93 hp C) 1.86 hp D) 0.740 hp
A
Find the net work done by friction on the body of a snake slithering in a complete circle of 3.93 m radius. The coefficient of friction between the ground and the snake is 0.25, and the snake's weight is 54.0 N. A) -330 J B) 0 J C) -3300 J D) -670 J
A
How long will it take a 7.08 hp motor to lift a 250 kg beam directly upward at constant velocity from the ground to a height of 45.0 m? Assume frictional forces are negligible. (1 hp = 746 W) A) 20.9 s B) 1.56 × 104 s C) 2.18 × 104 s D) 39.7 s
A
How much energy is needed to change the speed of a 1600 kg sport utility vehicle from 15.0 m/s to 40.0 m/s? A) 1.10 MJ B) 10.0 kJ C) 20.0 kJ D) 40.0 kJ E) 0.960 MJ
A
If electricity costs 6.00¢/kWh (kilowatt-hour), how much would it cost you to run a 120 W stereo system 4.0 hours per day for 4.0 weeks? A) $0.81 B) $0.12 C) $1.38 D) $2.27
A
In the figure, a 900-kg crate is on a rough surface inclined at 30°. A constant external force P = 7200 N is applied horizontally to the crate. While this force pushes the crate a distance of 3.0 m up the incline, its velocity changes from 1.2 m/s to 2.3 m/s. How much work does friction do during this process?A) -3700 J B) -7200 J C) +3700 J D) +7200 J E) zero
A
In the figure, two identical ideal massless springs have unstretched lengths of 0.25 m and spring constants of 700 N/m. The springs are attached to a small cube and stretched to a length L of 0.30 m as in Figure A. An external force P pulls the cube a distance D = 0.020 m to the right and holds it there. The external force P, that holds the cube in place in Figure B, is closest toA) 28 N. B) 25 N. C) 21 N. D) 18 N. E) 14 N
A
It requires 49 J of work to stretch an ideal very light spring from a length of 1.4 m to a length of 2.9 m. What is the value of the spring constant of this spring? A) 15 N/m B) 44 N/m C) 29 N/m D) 22 N/m
A
The International Space Station has a mass of 1.8 × 105 kg. A 70.0-kg astronaut inside the station pushes off one wall of the station so she accelerates at 1.50 m/s2. What is the magnitude of the acceleration of the space station as the astronaut is pushing off the wall? Give your answer relative to an observer who is space walking and therefore does not accelerate with the space station due to the push. A) 5.8 × 10-4 m/s2 B) 1.50 m/s2 C) 4.7 × 10-4 m/s2 D) zero E) 3.9 × 10-3 m/s2
A
The coefficient of the restitution of an object is defined as the ratio of its outgoing to incoming speed when the object collides with a rigid surface. For an object with a coefficient of 0.78, what fraction of the object's kinetic energy is lost during a single collision? A) 39% B) 16% C) 47% D) 61%
A
The work performed as a function of time for a process is given by W = at3 where a = 2.4 J/s3. What is the instantaneous power output at t = 3.7 s? A) 99 W B) 69 W C) 138 W D) 207 W
A
Two forces act on a 55-kg object. One force has magnitude 65 N directed 59° clockwise from the positive x-axis, and the other has a magnitude 35 N at 32° clockwise from the positive y-axis. What is the magnitude of this object's acceleration? A) 1.1 m/s2 B) 1.3 m/s2 C) 1.5 m/s2 D) 1.7 m/s2
A
You carry a 7.0 kg bag of groceries 1.2 m above the level floor at a constant velocity of 75 cm/s across a room that is 2.3m room. How much work do you do on the bag in the process? A) 0.0 J B) 82 J C) 158 J D) 134 J
A
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 identical conditions? A) It would have skidded 4 times farther. B) It would have skidded 2 times farther. C) It would have skidded times farther. D) It would have skidded 1/ times farther. E) It would have skidded 1/2 as far.
A
In a ballistics test, a 1.50-g bullet is fired through a 28.0-kg block traveling horizontally toward the bullet. In this test, the bullet takes 11.4 ms to pass through the block as it reverses the block's velocity from 1.75 m/s to the right to 1.20 m/s to the left with constant acceleration. Find the magnitude of the force that the bullet exerts on the block during this ballistics test.
Answer: 7.25 × 103 N
14) A potential energy function for system 1 is given by U1(x) = Cx2 + Bx3. The potential energy function for system 2 is given by U2(x) = A + Cx2 + Bx3, where A is a positive quantity. How does the force on system 1 relate to the force on system 2 at a given position? A) The force on the two systems will be in opposite directions. B) The force is identical on the two systems. C) The force on the second system will be with less than the force on the first system. D) There is no relationship between the forces on the two systems. E) The force on the second system will be with greater than the force on the first system.
B
4) Two identical balls are thrown directly upward, ball A at speed v and ball B at speed 2v, and they feel no air resistance. Which statement about these balls is correct? A) Ball B will go twice as high as ball A because it had twice the initial speed. B) Ball B will go four times as high as ball A because it had four times the initial kinetic energy. C) The balls will reach the same height because they have the same mass and the same acceleration. D) At its highest point, ball B will have twice as much gravitational potential energy as ball A because it started out moving twice as fast. E) At their highest point, the acceleration of each ball is instantaneously equal to zero because they stop for an instant.
B
A 20-ton truck collides with a 1500-lb car and causes a lot of damage to the car. During the collision A) the force on the truck due to the collision is slightly greater than the force on the car. B) the force of on the truck due to the collision is exactly equal to the force on the car. C) the force on the car due to the collision is much greater than the force on the truck. D) the car and the truck have the same magnitude acceleration.
B
A 7.0-kg object is acted on by two forces. One of the forces is 10.0 N acting toward the east. Which of the following forces is the other force if the acceleration of the object is 1.0 m/s2 toward the east? A) 6.0 N east B) 3.0 N west C) 12 N east D) 9.0 N west E) 7.0 N west
B
A box of mass m is pulled with a constant acceleration a along a horizontal frictionless floor by a wire that makes an angle of 15° above the horizontal. If T is the tension in this wire, then A) T = ma. B) T > ma. C) T < ma.
B
A fish weighing 16 N is weighed using two spring scales, each of negligible weight, as shown in the figure. What will be the readings of the scales? A) The bottom scale will read 16 N, and the top scale will read zero. B) Each scale will read 16 N. C) The top scale will read 16 N, and the bottom scale will read zero. D) The scales will have different readings, but the sum of the two readings will be 16 N. E) Each scale will read 8 N.
B
A force on a particle depends on position such that F(x) = (3.00 N/m2)x2 + (6.00 N/m)x for a particle constrained to move along the x-axis. What work is done by this force on a particle that moves from x = 0.00 m to x = 2.00 m? A) 10.0 J B) 20.0 J C) -48.0 J D) 24.0 J E) 48.0 J
B
Block A (0.40 kg) and block B (0.30 kg) are on a frictionless table (see figure). Spring 1 connects block A to a frictionless peg at 0 and spring 2 connects block A and block B. When the blocks are in uniform circular motion about 0, the springs have lengths of 0.60 m and 0.40 m, as shown. The springs are ideal and massless, and the linear speed of block B is 2.0 m/s. If the distance that spring 2 stretches is 0.060 m, the spring constant of spring 2 is closest to A) 18 N/m. B) 20 N/m. C) 22 N/m. D) 24 N/m. E) 26 N/m.
B
Bumpers on cars are not of much use in a collision. To see why, calculate the average force a bumper would have to exert if it brought a 1200-kg car (a so-called compact model) to a rest in 15 cm when the car had an initial speed of 2.0 m/s (about 4.5 mph). (Bumpers are built with springs that compress to provide a stopping force without, hopefully, denting the metal.) A) 1.8 × 104 N B) 1.6 × 104 N C) 5.4 × 104 N D) 6.5 × 105 N E) 3.2 × 104 N
B
Consider a plot of the displacement (x) as a function of the applied force (F) for an ideal elastic spring. The slope of the curve would be A) the spring constant. B) the reciprocal of the spring constant. C) the acceleration due to gravity. D) the reciprocal of the acceleration of gravity. E) the mass of the object attached to the spring.
B
Suppose you are playing hockey on a new-age ice surface for which there is no friction between the ice and the hockey puck. You wind up and hit the puck as hard as you can. After the puck loses contact with your stick, the puck will A) start to slow down. B) not slow down or speed up. C) speed up a little, and then slow down. D) speed up a little, and then move at a constant speed.
B
Two objects, one of mass m and the other of mass 2m, are dropped from the top of a building. When they hit the ground A) both of them will have the same kinetic energy. B) the heavier one will have twice the kinetic energy of the lighter one. C) the heavier one will have four times the kinetic energy of the lighter one. D) the heavier one will have times the kinetic energy of the lighter one.
B
You swing a bat and hit a heavy box with a force of 1500 N. The force the box exerts on the bat is A) exactly 1500 N only if the box does not move. B) exactly 1500 N whether or not the box moves. C) greater than 1500 N if the box moves. D) less than 1500 N if the box moves. E) greater than 1500 N if the bat bounces back.
B
10) A ball drops some distance and loses 30 J of gravitational potential energy. Do NOT ignore air resistance. How much kinetic energy did the ball gain? A) more than 30 J B) exactly 30 J C) less than 30 J
C
37) A potential energy function is given by U(x) = ( 3.00 N/m)x - ( 1.00 N/m3)x3. At what position or positions is the force equal to zero? A) m and - m B) 0.00 m, m and - m C) 1.00 m and -1.00 m D) 3.00 m and -3.00 m E) The force is not zero at any location.
C
38) The potential energy for a certain mass moving in one dimension is given by U(x) = (2.0 J/m3)x3 - (15 J/m2)x2 + (36 J/m)x - 23 J. Find the location(s) where the force on the mass is zero. A) 4.0 m, 5.0 m B) 1.0 m C) 2.0 m, 3.0 m D) 3.0 m, 5.0 m
C
A 10,000-kg rocket blasts off from earth with a uniform upward acceleration of 2.00 m/s2 and feels no air resistance. The upward thrust force its engines must provide during this acceleration is closest to A) 20,000 N. B) 980,000 N. C) 118,000 N. D) 78,000 N.
C
A 1000-kg car is driving toward the north along a straight horizontal road at a speed of 20.0 m/s. The driver applies the brakes and the car comes to a rest uniformly in a distance of 200 m. What are the magnitude and direction of the net force applied to the car to bring it to rest? A) 1.00 N north B) 10.0 × 103 N south C) 1.00 × 103 N south D) 1.00 N south E) 100 N south
C
A 4.0-kg object is moving with speed 2.0 m/s. A 1.0-kg object is moving with speed 4.0 m/s. Both objects encounter the same constant braking force, and are brought to rest. Which object travels the greater distance before stopping? A) the 4.0-kg object B) the 1.0-kg object C) Both objects travel the same distance. D) It is impossible to know without knowing how long each force acts.
C
A 5.00-kg box slides 4.00 m across the floor before coming to rest. What is the coefficient of kinetic friction between the floor and the box if the box had an initial speed of 3.00 m/s? A) 1.13 B) 0.587 C) 0.115 D) 0.229 E) 0.267
C
A constant horizontal pull acts on a sled on a horizontal frictionless ice pond. The sled starts from rest. When the pull acts over a distance x, the sled acquires a speed v and a kinetic energy K. If the same pull instead acts over twice this distance: A) The sled's speed will be 2v and its kinetic energy will be 2K. B) The sled's speed will be 2v and its kinetic energy will be K. C) The sled's speed will be v and its kinetic energy will be 2K. D) The sled's speed will be v and its kinetic energy will be K. E) The sled's speed will be 4v and its kinetic energy will be 2K.
C
You are seated in a bus and notice that a hand strap that is hanging from the ceiling hangs away from the vertical in the backward direction. From this observation, you can conclude that A) the velocity of the bus is forward. B) the velocity of the bus is backward. C) You cannot conclude anything about the direction of the velocity of the bus.
C
11) Block 1 and block 2 have the same mass, m, and are released from the top of two inclined planes of the same height making 30° and 60° angles with the horizontal direction, respectively. If the coefficient of friction is the same in both cases, which of the blocks is going faster when it reaches the bottom of its respective incline? A) We must know the actual masses of the blocks to answer. B) Both blocks have the same speed at the bottom. C) Block 1 is faster. D) Block 2 is faster. E) There is not enough information to answer the question because we do not know the value of the coefficient of kinetic friction.
D
13) Which, if any, of the following statements concerning the work done by a conservative force is NOT true? A) It can always be expressed as the difference between the initial and final values of a potential energy function. B) It is independent of the path of the body and depends only on the starting and ending points. C) When the starting and ending points are the same, the total work is zero. D) All of the above statements are true. E) None of the above statements are true.
D
17) Consider the motion of a 1.00-kg particle that moves with potential energy given by U(x) = (-2.00 J∙m)/x + (4.00 J∙m2)/x2. Suppose the particle is moving with a speed of 3.00 m/s when it is located at x = 1.00 m. What is the speed of the object when it is located at x = 5.00 m? A) 2.13 m/s B) 3.00 m/s C) 4.68 m/s D) 3.67 m/s
D
19) A projectile is fired from ground level at an angle of 40.0° above horizontal at a speed of 30.0 m/s. What is the speed of the projectile when it has reached a height equal to 50.0% of its maximum height? A) 26.0 m/s B) 27.4 m/s C) 28.7 m/s D) 26.7 m/s E) 28.1 m/s
D
20) A very small 100-g object is attached to one end of a massless 10-cm rod that is pivoted without friction about the opposite end. The rod is held vertical, with the object at the top, and released, allowing the rod to swing. What is the speed of the object at the instant that the rod is horizontal? A) 0.71 m/s B) 4.0 m/s C) 1.4 m/s D) 2.8 m/s E) 2.8 m/s
D
3) Two stones, one of mass m and the other of mass 2m, are thrown directly upward with the same velocity at the same time from ground level and feel no air resistance. Which statement about these stones is true? A) The heavier stone will go twice as high as the lighter one because it initially had twice as much kinetic energy. B) Both stones will reach the same height because they initially had the same amount of kinetic energy. C) At their highest point, both stones will have the same gravitational potential energy because they reach the same height. D) At its highest point, the heavier stone will have twice as much gravitational potential energy as the lighter one because it is twice as heavy. E) The lighter stone will reach its maximum height sooner than the heavier one.
D
A 3.00-kg ball swings rapidly in a complete vertical circle of radius 2.00 m by a light string that is fixed at one end. The ball moves so fast that the string is always taut and perpendicular to the velocity of the ball. As the ball swings from its lowest point to its highest point A) the work done on it by gravity and the work done on it by the tension in the string are both equal to -118 J. B) the work done on it by gravity is -118 J and the work done on it by the tension in the string is +118 J. C) the work done on it by gravity is +118 J and the work done on it by the tension in the string is -118 J. D) the work done on it by gravity is -118 J and the work done on it by the tension in the string is zero. E) the work done on it by gravity and the work done on it by the tension in the string are both equal to zero.
D
A 4.00-kg mass is attached to a very light ideal spring hanging vertically and hangs at rest in the equilibrium position. The spring constant of the spring is 1.00 N/cm. The mass is pulled downward 2.00 cm and released. What is the speed of the mass when it is 1.00 cm above the point from which it was released? A) 0.0443 m/s B) 0.0744 m/s C) 0.0201 m/s D) 0.0866 m/s E) The mass will not reach the height specified.
D
A stock person at the local grocery store has a job consisting of the following five segments: (1) picking up boxes of tomatoes from the stockroom floor (2) accelerating to a comfortable speed (3) carrying the boxes to the tomato display at constant speed (4) decelerating to a stop (5) lowering the boxes slowly to the floor. During which of the five segments of the job does the stock person do positive work on the boxes? A) (1) and (5) B) (1) only C) (1), (2), (4), and (5) D) (1) and (2) E) (2) and (3)
D
A student slides her 80.0-kg desk across the level floor of her dormitory room a distance 4.00 m at constant speed. If the coefficient of kinetic friction between the desk and the floor is 0.400, how much work did she do? A) 128 J B) 3.14 kJ C) 26.7 J D) 1.26 kJ E) 24.0 J
D
A worker lifts a 20.0-kg bucket of concrete from the ground up to the top of a 20.0-m tall building. The bucket is initially at rest, but is traveling at 4.0 m/s when it reaches the top of the building. What is the minimum amount of work that the worker did in lifting the bucket? A) 3.92 kJ B) 400 J C) 560 J D) 4.08 kJ E) 160 J
D
Consider what happens when you jump up in the air. Which of the following is the most accurate statement? A) It is the upward force exerted by the ground that pushes you up, but this force cannot exceed your weight. B) You are able to spring up because the earth exerts a force upward on you that is greater than the downward force you exert on the earth. C) Since the ground is stationary, it cannot exert the upward force necessary to propel you into the air. Instead, it is the internal forces of your muscles acting on your body itself that propels your body into the air. D) When you push down on the earth with a force greater than your weight, the earth will push back with the same magnitude force and thus propel you into the air. E) When you jump up the earth exerts a force F1 on you and you exert a force F2 on the earth. You go up because F1 > F2.
D
If a 5.0 kg box is pulled simultaneously by a 10.0 N force and a 5.0 N force, then its acceleration must be A) 3.0 m/s2. B) 2.2 m/s2. C) 1.0 m/s2. D) We cannot tell from the information given
D
On its own, a certain tow-truck has a maximum acceleration of 3.0 m/s2. What would be the maximum acceleration when this truck was towing a bus of twice its own mass? A) 2.5 m/s2 B) 2.0 m/s2 C) 1.5 m/s2 D) 1.0 m/s2
D
The following four forces act on a 4.00 kg object: 1) 300N East 2) 700N North 3) 500N West 4) 600N NorthWhat is the acceleration of the object? A) 224 N in a direction 63.4° north of west B) 300 N in a direction 63.4° north of west C) 300 N in a direction 26.6° north of west D) 224 N in a direction 26.6° north of west E) 2100 N in a direction 26.6° north of west
D
12) A girl throws a stone from a bridge. Consider the following ways she might throw the stone. The speed of the stone as it leaves her hand is the same in each case, and air resistance is negligible. Case A: Thrown straight up. Case B: Thrown straight down. Case C: Thrown out at an angle of 45° above horizontal. Case D: Thrown straight out horizontally. In which case will the speed of the stone be greatest when it hits the water below? A) Case A B) Case B C) Case C D) Case D E) The speed will be the same in all cases.
E
A 1500-kg car accelerates from 0 to 25 m/s in 7.0 s with negligible friction and air resistance. What is the average power delivered by the engine? (1 hp = 746 W) A) 50 hp B) 60 hp C) 70 hp D) 80 hp E) 90 hp
E
An unusual spring has a restoring force of magnitude F = (2.00 N/m)x + (1.00 N/m2)x2, where x is the stretch of the spring from its equilibrium length. A 3.00-kg object is attached to this spring and released from rest after stretching the spring 1.50 m. If the object slides over a frictionless horizontal surface, how fast is it moving when the spring returns to its equilibrium length? A) 2.06 m/s B) 4.33 m/s C) 3.27 m/s D) 5.48 m/s E) 1.50 m/s
E
On a horizontal frictionless floor, a worker of weight 0.900 kN pushes horizontally with a force of 0.200 kN on a box weighing 1.80 kN. As a result of this push, which statement could be true? A) The box will not move because the push is less than its weight. B) The worker and box will both have an acceleration of 1.08 m/s2, but in opposite directions. C) The worker and box will both have an acceleration of 2.17 m/s2, but in opposite directions. D) The worker will accelerate at 1.08 m/s2 and the box will accelerate at 2.17 m/s2, but in opposite directions. E) The worker will accelerate at 2.17 m/s2 and the box will accelerate at 1.08 m/s2, but in opposite directions.
E
Two men, Joel and Jerry, push against a wall. Jerry stops after 10 min, while Joel is able to push for 5.0 min longer. Compare the work they do. A) Both men do positive work, but Joel does 75% more work than Jerry. B) Both men do positive work, but Joel does 50% more work than Jerry. C) Both men do positive work, but Jerry does 50% more work than Joel. D) Both men do positive work, but Joel does 25% more work than Jerry. E) Neither of them does any work
E
You are standing in a moving bus, facing forward, and you suddenly fall forward as the bus comes to an immediate stop. The force acting on you that causes you to fall forward is A) the force of gravity. B) the normal force due to your contact with the floor of the bus. C) the force due to static friction between you and the floor of the bus. D) the force due to kinetic friction between you and the floor of the bus. E) No forces were acting on you to cause you to fall.
E
A car is being towed at constant velocity on a horizontal road using a horizontal chain. The tension in the chain must be equal to the weight of the car in order to maintain constant velocity. A) True B) False
False
In order to get an object moving, you must push harder on it than it pushes back on you. A) True B) False
False
In order to lift a bucket of concrete, you must pull up harder on the bucket than it pulls down on you. A) True B) False
False
Two objects, each of weight W, hang vertically by spring scales as shown in the figure. The pulleys and the strings attached to the objects have negligible weight, and there is no appreciable friction in the pulleys. The reading in each scale isA) W. B) more than W, but not quite twice as much. C) less than W. D) 2W. E) more than 2W.
W
