Question 1

Which of the following is NOT a correct unit for work?

Accepted Answer

A)  erg 
B)  ft.lb 
C)  watt 
D)  newton.meter 
E)  joule 
A)  erg 
B)  ft.lb 
C)  watt 
D)  newton.meter 
E)  joule

Question 2

Which of the following is the correct combination of dimensions for energy?

Accepted Answer

A)  MLT 
B)  LT2 /M 
C)  ML2/T2 
D)  M2L3T 
E)  ML/T2 
A)  MLT 
B)  LT2 /M 
C)  ML2/T2 
D)  M2L3T 
E)  ML/T2

Question 3

A 0.50-kg object moves in a horizontal circular track with a radius of 2.5 m. An external force of 3.0 N, always tangent to the track, causes the object to speed up as it goes around. The work done by the external force as the mass makes one revolution is:

Accepted Answer

A)  24 J 
B)  47 J 
C)  59 J 
D)  94 J 
E)  120 J 
A)  24 J 
B)  47 J 
C)  59 J 
D)  94 J 
E)  120 J

Question 4

A 2-kg object is moving at 3 m/s. A 4-N force is applied in the direction of motion and then removed after the object has traveled an additional 5 m. The work done by this force is:

Accepted Answer

A)  12 J 
B)  15 J 
C)  18 J 
D)  20 J 
E)  38 J 
A)  12 J 
B)  15 J 
C)  18 J 
D)  20 J 
E)  38 J

Question 5

A 2-kg block is attached to a horizonal ideal spring with a spring constant of 200 N/m. When the has its equilibrium length the block is given a speed of 5 m/s. What is the maximum elongation of the spring?

Accepted Answer

A)  0 
B)  0.05 m 
C)  5 m 
D)  10 m 
E)  100 m 
A)  0 
B)  0.05 m 
C)  5 m 
D)  10 m 
E)  100 m

Question 6

An object moves in a circle at constant speed. The work done by the centripetal force is zero because:

Accepted Answer

A)  the displacement for each revolution is zero 
B)  the average force for each revolution is zero 
C)  there is no friction 
D)  the magnitude of the acceleration is zero 
E)  the centripetal force is perpendicular to the velocity 
A)  the displacement for each revolution is zero 
B)  the average force for each revolution is zero 
C)  there is no friction 
D)  the magnitude of the acceleration is zero 
E)  the centripetal force is perpendicular to the velocity

Question 7

Two objects with masses, m1 and m2, have the same kinetic energy and are both moving to the right. The same constant force   is applied to the left to both masses. If m1 = 4m2, the ratio of the stopping distance of m1 to that of m2 is:

Accepted Answer

A)  1:4 
B)  4:1 
C)  1:2 
D)  2:1 
E)  1:1 
A)  1:4 
B)  4:1 
C)  1:2 
D)  2:1 
E)  1:1

Question 8

A watt per hour is a unit of:

Accepted Answer

A)  energy 
B)  power 
C)  force 
D)  acceleration 
E)  none of these 
A)  energy 
B)  power 
C)  force 
D)  acceleration 
E)  none of these

Question 9

A crate is initially at rest on a horizontal frictionless table. A constant horizontal force F is applied. Which of the following five graphs is a correct plot of work W as a function of crate speed v?

Accepted Answer

A)  I 
B)  II 
C)  III 
D)  IV 
E)  V 
A)  I 
B)  II 
C)  III 
D)  IV 
E)  V

Question 10

Power has the dimensions of:

Accepted Answer

A)  ML2/T2 
B)  MT/L2 
C)  ML/T2 
D)  ML2/T3 
E)  none of these 
A)  ML2/T2 
B)  MT/L2 
C)  ML/T2 
D)  ML2/T3 
E)  none of these

Question 11

A 50-N force acts on a 2-kg crate that starts from rest. When the force has been acting for 2 s the rate at which it is doing work is:

Accepted Answer

A)  75 W 
B)  100 W 
C)  1000 W 
D)  2500 W 
E)  5000 W 
A)  75 W 
B)  100 W 
C)  1000 W 
D)  2500 W 
E)  5000 W

Question 12

A line drive to the shortstop is caught at the same height as it was originally hit. Over its entire flight the work done by gravity and the work done by air resistance, respectively, are:

Accepted Answer

A)  zero; positive 
B)  zero; negative 
C)  positive; negative 
D)  negative; positive 
E)  negative; negative 
A)  zero; positive 
B)  zero; negative 
C)  positive; negative 
D)  negative; positive 
E)  negative; negative

Question 13

A Boston Red Sox baseball player catches a ball of mass m that is moving toward him with speed v. While bringing the ball to rest, his hand moves back a distance d. Assuming constant deceleration, the horizontal force exerted on the ball by his hand is:

Accepted Answer

A)  mv/d 
B)  mvd 
C)  mv2/d 
D)  2mv/d 
E)  mv2/(2d) 
A)  mv/d 
B)  mvd 
C)  mv2/d 
D)  2mv/d 
E)  mv2/(2d)

Question 14

An 80-N crate slides with constant speed a distance of 5.0 m downward along a rough slope that makes an angle of 30 $\degree$ with the horizontal. The work done by the force of gravity is:

Accepted Answer

A)  -400 J 
B)  -200 J 
C)  -69 J 
D)  200 J 
E)  400 J 
A)  -400 J 
B)  -200 J 
C)  -69 J 
D)  200 J 
E)  400 J

Question 15

A man pulls a 100-N crate up a frictionless 30 ° slope 5 m high as shown. Assuming that the crate moves at constant speed, the work done by the man is:

Accepted Answer

A)  -500 J 
B)  -250 J 
C)  0 
D)  250 J 
E)  500 J 
A)  -500 J 
B)  -250 J 
C)  0 
D)  250 J 
E)  500 J

Question 16

The work done by gravity during the descent of a projectile is:

Accepted Answer

A)  positive 
B)  negative 
C)  zero 
D)  depends for its sign on the direction of the y axis 
E)  depends for its sign on the direction of both the x and y axes 
A)  positive 
B)  negative 
C)  zero 
D)  depends for its sign on the direction of the y axis 
E)  depends for its sign on the direction of both the x and y axes

Question 17

A 8000-N car is traveling at 12 m/s along a horizontal road when the brakes are applied. The car skids to a stop in 4.0 s. How much kinetic energy does the car lose in this time?

Accepted Answer

A)  4.8 * 104 J 
B)  5.9 *104 J 
C)  1.2 * 105 J 
D)  5.8 * 105 J 
E)  4.8* 106 J 
A)  4.8 * 104 J 
B)  5.9 *104 J 
C)  1.2 * 105 J 
D)  5.8 * 105 J 
E)  4.8* 106 J

Question 18

The mechanical advantage of any machine is:

Accepted Answer

A)  the efficiency of the machine 
B)  the work done by the machine 
C)  the ratio of the work done by the machine to the work expended on it 
D)  the ratio of the force exerted by the machine to the force applied to it 
E)  the ratio of the force applied to the machine to the force exerted by it 
A)  the efficiency of the machine 
B)  the work done by the machine 
C)  the ratio of the work done by the machine to the work expended on it 
D)  the ratio of the force exerted by the machine to the force applied to it 
E)  the ratio of the force applied to the machine to the force exerted by it

Question 19

A man wishes to pull a crate 15 m across a rough floor by exerting a force of 100 N. The coefficient of kinetic friction is 0.25. For the man to do the least work, the angle between the force and the horizontal should be:

Accepted Answer

A)  0 
B)  14 ° 
C)  43 ° 
D)  66 ° 
E)  76 ° 
A)  0 
B)  14 ° 
C)  43 ° 
D)  66 ° 
E)  76 °

Question 20

A boy holds a 40-N weight at arm's length for 10 s. His arm is 1.5 m above the ground. The work done by the force of the boy on the weight while he is holding it is:

Accepted Answer

A)  0 
B)  6.1 J 
C)  40 J 
D)  60 J 
E)  90 J 
A)  0 
B)  6.1 J 
C)  40 J 
D)  60 J 
E)  90 J

Exam 7: Kinetic Energy and Work

Which of the following is NOT a correct unit for work?

Which of the following is the correct combination of dimensions for energy?

A 0.50-kg object moves in a horizontal circular track with a radius of 2.5 m. An external force of 3.0 N, always tangent to the track, causes the object to speed up as it goes around. The work done by the external force as the mass makes one revolution is:

A 2-kg object is moving at 3 m/s. A 4-N force is applied in the direction of motion and then removed after the object has traveled an additional 5 m. The work done by this force is:

A 2-kg block is attached to a horizonal ideal spring with a spring constant of 200 N/m. When the has its equilibrium length the block is given a speed of 5 m/s. What is the maximum elongation of the spring?

An object moves in a circle at constant speed. The work done by the centripetal force is zero because:

Two objects with masses, m1 and m2, have the same kinetic energy and are both moving to the right. The same constant force is applied to the left to both masses. If m1 = 4m2, the ratio of the stopping distance of m1 to that of m2 is:

A watt per hour is a unit of:

A crate is initially at rest on a horizontal frictionless table. A constant horizontal force F is applied. Which of the following five graphs is a correct plot of work W as a function of crate speed v?

Power has the dimensions of:

A 50-N force acts on a 2-kg crate that starts from rest. When the force has been acting for 2 s the rate at which it is doing work is:

A line drive to the shortstop is caught at the same height as it was originally hit. Over its entire flight the work done by gravity and the work done by air resistance, respectively, are:

A Boston Red Sox baseball player catches a ball of mass m that is moving toward him with speed v. While bringing the ball to rest, his hand moves back a distance d. Assuming constant deceleration, the horizontal force exerted on the ball by his hand is:

An 80-N crate slides with constant speed a distance of 5.0 m downward along a rough slope that makes an angle of 30 °\degree° with the horizontal. The work done by the force of gravity is:

A man pulls a 100-N crate up a frictionless 30 ° slope 5 m high as shown. Assuming that the crate moves at constant speed, the work done by the man is:

The work done by gravity during the descent of a projectile is:

A 8000-N car is traveling at 12 m/s along a horizontal road when the brakes are applied. The car skids to a stop in 4.0 s. How much kinetic energy does the car lose in this time?

The mechanical advantage of any machine is:

A man wishes to pull a crate 15 m across a rough floor by exerting a force of 100 N. The coefficient of kinetic friction is 0.25. For the man to do the least work, the angle between the force and the horizontal should be:

A boy holds a 40-N weight at arm's length for 10 s. His arm is 1.5 m above the ground. The work done by the force of the boy on the weight while he is holding it is:

Measurement

Motion Along a Straight Line

Vector

Motion in Two and Three Dimensions

Force and Motion I

Force and Motion II

Potential Energy and Conservation of Energy

Center of Mass and Linear Momentum

Rotation

Rolling, Torque, and Angular Momentum

Equilibrium and Elasticity

Gravitation

Fluids

Oscillations

Waves I

Waves II

Temperature, Heat, and the First Law of Thermodynamics

The Kinetic Theory of Gases

Entropy and the Second Law of Thermodynamics

Electric Charge

Electric Fields

Gauss Law

Electric Potential

Capacitance

Current and Resistance

Circuits

Magnetic Fields

Magnetic Fields Due to Currents

Induction and Inductance

Electromagnetic Oscillations and Alternating Current

Maxwells Equations; Magnetism of Matter

Electromagnetic Waves

Images

Interference

Diffraction

Relativity

Photons and Matter Waves

More About Matter Waves

All About Atoms

Conduction of Electricity in Solids

Nuclear Physics

Energy From the Nucleus

Quarks, Leptons, and the Big Bang

Filters

Two objects with masses, m₁ and m₂, have the same kinetic energy and are both moving to the right. The same constant force is applied to the left to both masses. If m₁ = 4m₂, the ratio of the stopping distance of m₁ to that of m₂ is:

An 80-N crate slides with constant speed a distance of 5.0 m downward along a rough slope that makes an angle of 30 $\degree$ with the horizontal. The work done by the force of gravity is: