Question 1

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 2.3 m room.How much work do you do on the bag in the process?

Accepted Answer

A)  0.0 J 
B)  82 J 
C)  158 J 
D)  134 J 
A)  0.0 J 
B)  82 J 
C)  158 J 
D)  134 J

Question 2

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?

Accepted Answer

A)  619 J 
B)  826 J 
C)  495 J 
D)  925 J 
A)  619 J 
B)  826 J 
C)  495 J 
D)  925 J

Question 3

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.

Accepted Answer

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. 
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.

Question 4

If a force always acts perpendicular to an object's direction of motion,that force cannot change the object's kinetic energy.

Accepted Answer

A) True 
 B)False

Question 5

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?

Accepted Answer

A)  423 J 
B)  4230 kJ 
C)  423 kJ 
D)  4230 J 
A)  423 J 
B)  4230 kJ 
C)  423 kJ 
D)  4230 J

Question 6

A 60.0-kg person drops from rest a distance of 1.20 m to a platform of negligible mass supported by an ideal stiff spring of negligible mass.The platform drops 6.00 cm before the person comes to rest.What is the spring constant of the spring?

Accepted Answer

A)  2.56 × 105 N/m 
B)  3.92 × 105 N/m 
C)  5.45 × 104 N/m 
D)  4.12 × 105 N/m 
E)  8.83 × 104 N/m 
A)  2.56 × 105 N/m 
B)  3.92 × 105 N/m 
C)  5.45 × 104 N/m 
D)  4.12 × 105 N/m 
E)  8.83 × 104 N/m

Question 7

An object is attached to a hanging unstretched ideal and massless spring and slowly lowered to its equilibrium position,a distance of 6.4 cm below the starting point.If instead of having been lowered slowly the object was dropped from rest,how far then would it then stretch the spring at maximum elongation?

Accepted Answer

A)  13 cm 
B)  9.1 cm 
C)  6.4 cm 
D)  18 cm 
E)  26 cm 
A)  13 cm 
B)  9.1 cm 
C)  6.4 cm 
D)  18 cm 
E)  26 cm

Question 8

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?

Accepted Answer

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 
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

Question 9

When an object is solely under the influence of conservative forces,the sum of its kinetic and potential energies does not change.

Accepted Answer

A) True 
 B)False

Question 10

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

Accepted Answer

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. 
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.

Question 11

Swimmers at a water park have a choice of two frictionless water slides as shown in the figure.Although both slides drop over the same height,h,slide 1 is straight while slide 2 is curved,dropping quickly at first and then leveling out.How does the speed v1 of a swimmer reaching the end of slide 1 compares with v2,the speed of a swimmer reaching the end of slide 2?

Accepted Answer

A)  v1 > v2 
B)  v1 2 
C)  v1 = v2 
D)  No simple relationship exists between v1 and v2 because we do not know the curvature of slide 2. 
A)  v1 > v2 
B)  v1 2 
C)  v1 = v2 
D)  No simple relationship exists between v1 and v2 because we do not know the curvature of slide 2.

Question 12

In the figure,two identical springs have unstretched lengths of 0.25 m and spring constants of 300 N/m.The springs are attached to a small cube and stretched to a length L of 0.36 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.(See Figure B.)The work done by the external force P in pulling the cube 0.020 m is closest to

Accepted Answer

A)  0.12 J. 
B)  0.060 J. 
C)  6.0 J. 
D)  12 J. 
E)  0.80 J. 
A)  0.12 J. 
B)  0.060 J. 
C)  6.0 J. 
D)  12 J. 
E)  0.80 J.

Question 13

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?

Accepted Answer

A)  more than 30 J 
B)  exactly 30 J 
C)  less than 30 J 
A)  more than 30 J 
B)  exactly 30 J 
C)  less than 30 J

Question 14

A box of mass m is pressed against (but is not attached to)an ideal spring of force constant k and negligible mass,compressing the spring a distance x.After it is released,the box slides up a frictionless incline as shown in the figure and eventually stops.If we repeat this experiment but instead compress the spring a distance of 2x

Accepted Answer

A)  the box will go up the incline twice as high as before. 
B)  just as it moves free of the spring, the box will be traveling twice as fast as before. 
C)  just as it moves free of the spring, the box will be traveling four times as fast as before. 
D)  just as it moves free of the spring, the box will have twice as much kinetic energy as before. 
E)  just before it is released, the box has twice as much elastic potential energy as before. 
A)  the box will go up the incline twice as high as before. 
B)  just as it moves free of the spring, the box will be traveling twice as fast as before. 
C)  just as it moves free of the spring, the box will be traveling four times as fast as before. 
D)  just as it moves free of the spring, the box will have twice as much kinetic energy as before. 
E)  just before it is released, the box has twice as much elastic potential energy as before.

Question 15

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)

Accepted Answer

A)  20.9 s 
B)  1.56 × 104 s 
C)  2.18 × 104 s 
D)  39.7 s 
A)  20.9 s 
B)  1.56 × 104 s 
C)  2.18 × 104 s 
D)  39.7 s

Question 16

An 8.0-g bullet is shot into a 4.0-kg block,at rest on a frictionless horizontal surface (see the figure).The bullet remains lodged in the block.The block moves into an ideal massless spring and compresses it by 8.7 cm.The spring constant of the spring is 2400 N/m.The initial velocity of the bullet is closest to

Accepted Answer

A)  1100 m/s. 
B)  1200 m/s. 
C)  900 m/s. 
D)  1300 m/s. 
E)  1000 m/s. 
A)  1100 m/s. 
B)  1200 m/s. 
C)  900 m/s. 
D)  1300 m/s. 
E)  1000 m/s.

Question 17

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.

Accepted Answer

Question 18

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?

Accepted Answer

A)  15 N/m 
B)  44 N/m 
C)  29 N/m 
D)  22 N/m 
A)  15 N/m 
B)  44 N/m 
C)  29 N/m 
D)  22 N/m

Question 19

The force on a 3.00-kg object as a function of position is shown in the figure. If an object is moving at 2.50 m/s when it is located at x = 2.00 m,what will its speed be when it reaches x = 8.00 m? (Assume that the numbers on the graph are accurate to 3 significant figures.)

Accepted Answer

A)  3.25 m/s 
B)  3.70 m/s 
C)  4.10 m/s 
D)  2.90 m/s 
E)  4.50 m/s 
A)  3.25 m/s 
B)  3.70 m/s 
C)  4.10 m/s 
D)  2.90 m/s 
E)  4.50 m/s

Question 20

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?

Accepted Answer

A)  3.92 kJ 
B)  400 J 
C)  560 J 
D)  4.08 kJ 
E)  160 J 
A)  3.92 kJ 
B)  400 J 
C)  560 J 
D)  4.08 kJ 
E)  160 J

Exam 9: Work

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 2.3 m room.How much work do you do on the bag in the process?

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.

If a force always acts perpendicular to an object's direction of motion,that force cannot change the object's kinetic energy.

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 60.0-kg person drops from rest a distance of 1.20 m to a platform of negligible mass supported by an ideal stiff spring of negligible mass.The platform drops 6.00 cm before the person comes to rest.What is the spring constant of the spring?

When an object is solely under the influence of conservative forces,the sum of its kinetic and potential energies does not change.

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 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?

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 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.

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?

The force on a 3.00-kg object as a function of position is shown in the figure. If an object is moving at 2.50 m/s when it is located at x = 2.00 m,what will its speed be when it reaches x = 8.00 m? (Assume that the numbers on the graph are accurate to 3 significant figures.)

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?

Foundations

A: Foundations

Motion in One Dimension

Acceleration

Momentum

Energy

Principle of Relativity

Interactions

Force

Motion in a Plane

Motion in a Circle

Torque

Gravity

Special Relativity

Periodic Motion

Waves in One Dimension

Waves in Two and Three Dimensions

Fluids

Entropy

Energy Transferred Thermally

Degradation of Energy

Electric Interactions

The Electric Field

Gausss Law

Work and Energy in Electrostatics

Charge Separation and Storage

Magnetic Interactions

Magnetic Fields of Charged Particles in Motion

Changing Magnetic Fields

Changing Electric Fields

Electric Circuits

Electronics

Ray Optics

Wave and Particle Optics

Filters

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.