Question 1

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) 100 W 
B) 1000 W 
C) 2500 W 
D) 5000 W 
E) 63000 W 
A) 100 W 
B) 1000 W 
C) 2500 W 
D) 5000 W 
E) 63000 W C

Question 2

A crate moves 10 m to the right on a horizontal surface as a woman pulls on it with a 10-N force.Rank the situations shown below according to the work done by her force, least to greatest.

Accepted Answer

A) 1,2,3 
B) 2,1,3 
C) 2,3,1 
D) 1,3,2 
E) 3,2,1, 
A) 1,2,3 
B) 2,1,3 
C) 2,3,1 
D) 1,3,2 
E) 3,2,1, E

Question 3

Which of the following five quantities is NOT an expression for energy? Here m is a mass, g is the acceleration due to gravity, h and d are distances, F is a force, v is a speed, a is an acceleration, P is power, and t is time.

Accepted Answer

A) mgh 
B) Fd 
C) 1/2mv2 
D) ma 
E) Pt 
A) mgh 
B) Fd 
C) 1/2mv2 
D) ma 
E) Pt D

Question 4

A man pushes an 80-N crate a distance of 5.0 m upward along a frictionless slope that makes an angle of 30$\degree$with the horizontal.The force he exerts is parallel to the slope.If the speed of the crate is constant, then the work done by the man is:

Accepted Answer

A) -200 J 
B) 61 J 
C) 140 J 
D) 200 J 
E) 260 J 
A) -200 J 
B) 61 J 
C) 140 J 
D) 200 J 
E) 260 J

Question 5

Which of the following five units represents a quantity that is NOT the same type as the other four?

Accepted Answer

A) joule 
B) erg 
C) watt 
D) foot.pound 
E) newton.meter 
A) joule 
B) erg 
C) watt 
D) foot.pound 
E) newton.meter

Question 6

At time t = 0 a particle starts moving along the x axis.If its kinetic energy increases uniformly with t the net force acting on it must be:

Accepted Answer

A) constant 
B) proportional to t 
C) inversely proportional to t 
D) proportional to 
E) proportional to 1/ 
A) constant 
B) proportional to t 
C) inversely proportional to t 
D) proportional to 
E) proportional to 1/

Question 7

Two trailers, X with mass 500 kg and Y with mass 2000 kg, are being pulled at the same speed.The ratio of the kinetic energy of Y to that of X is:

Accepted Answer

A) 1:1 
B) 2:1 
C) 4:1 
D) 9:1 
E) 1500:1 
A) 1:1 
B) 2:1 
C) 4:1 
D) 9:1 
E) 1500:1

Question 8

A particle moves 5 m in the positive x direction while being acted upon by a constant force = (4 N)+ (2 N)- (4 N).The work done on the particle by this force is:

Accepted Answer

A) 20 J 
B) 10 J 
C) -20 J 
D) 30 J 
E) is impossible to calculate without knowing other forces 
A) 20 J 
B) 10 J 
C) -20 J 
D) 30 J 
E) is impossible to calculate without knowing other forces

Question 9

Three identical springs (X, Y, Z)are arranged as shown.When a 4.0-kg mass is hung on X, the mass descends 3.0 cm.When a 6.0-kg mass is hung on Y, the mass descends:

Accepted Answer

A) 2.0 cm 
B) 4.0 cm 
C) 4.5 cm 
D) 6.0 cm 
E) 9.0 cm 
A) 2.0 cm 
B) 4.0 cm 
C) 4.5 cm 
D) 6.0 cm 
E) 9.0 cm

Question 10

When a certain rubber band is stretched a distance x, it exerts a restoring force F = ax + bx2, where a and b are constants.The work done in stretching this rubber band from x = 0 to x = L is:

Accepted Answer

A) aL2 + bLx3 
B) aL + 2bL2 
C) a + 2bL 
D) bL 
E) aL2/2 + bL3/3 
A) aL2 + bLx3 
B) aL + 2bL2 
C) a + 2bL 
D) bL 
E) aL2/2 + bL3/3

Question 11

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) 9 J 
B) 18 J 
C) 20 J 
D) 29 J 
E) 38 J 
A) 9 J 
B) 18 J 
C) 20 J 
D) 29 J 
E) 38 J

Question 12

An object is constrained by a cord to move in a circular path of radius 0.5m on a horizontal frictionless surface.The cord will break if its tension exceeds 16N.The maximum kinetic energy the object can have is:

Accepted Answer

A) 4 J 
B) 8 J 
C) 16 J 
D) 32 J 
E) 64 J 
A) 4 J 
B) 8 J 
C) 16 J 
D) 32 J 
E) 64 J

Question 13

An 8-N block slides down an incline.It has an initial speed of 7 m/s.The work done by the resultant force on this block is:

Accepted Answer

A) 20 J 
B) 28 J 
C) 56 J 
D) impossible to calculate without more information 
E) none of these 
A) 20 J 
B) 28 J 
C) 56 J 
D) impossible to calculate without more information 
E) none of these

Question 14

A man moves the 10-g object shown in a vertical plane at a constant speed from position X to position Y along a circular track of radius 20 m.The process takes 0.75 min.The work done by the man is about:

Accepted Answer

A) 1 J 
B) 2 J 
C) 4 J 
D) 6 J 
E) 12 J 
A) 1 J 
B) 2 J 
C) 4 J 
D) 6 J 
E) 12 J

Question 15

A man pushes an 80-N crate a distance of 5.0 m upward along a frictionless slope that makes an angle of 30$\degree$with the horizontal.His force is parallel to the slope.If the speed of the crate decreases at a rate of 1.5 m/s2, then the work done by the man is:

Accepted Answer

A) -200 J 
B) 61 J 
C) 140 J 
D) 200 J 
E) 400 J 
A) -200 J 
B) 61 J 
C) 140 J 
D) 200 J 
E) 400 J

Question 16

When a certain rubber band is stretched a distance x, it exerts a restoring force of magnitude F = Ax, where A is a constant.The work done by a person in stretching this rubber band from x = 0 to x = L is:

Accepted Answer

A) AL2 
B) AL 
C) A + 2L2 
D) A/L 
E) AL2/2 
A) AL2 
B) AL 
C) A + 2L2 
D) A/L 
E) AL2/2

Question 17

One watt is:

Accepted Answer

A) 1 kg . m/s3 
B) 1 kg . m2/s 
C) 1 kg . m2/s3 
D) 1 kg. m/s 
E) 1 kg . m2/s2 
A) 1 kg . m/s3 
B) 1 kg . m2/s 
C) 1 kg . m2/s3 
D) 1 kg. m/s 
E) 1 kg . m2/s2

Question 18

A force = (4.1 N)+ (2.6 N)- (4.7 N)acts on a mass of 2.3 kg as it moves in the x direction at a speed of 7.2 m/s.What is the rate at which the force is doing work?

Accepted Answer

A) 8.8 W 
B) 16 W 
C) 30 W 
D) 49 W 
E) 60 W 
A) 8.8 W 
B) 16 W 
C) 30 W 
D) 49 W 
E) 60 W

Question 19

A 2-kg block is attached to a horizontal ideal spring with a spring constant of 200 N/m.When the spring 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 m 
B) 0.5 m 
C) 5 m 
D) 10 m 
E) 100 m 
A) 0 m 
B) 0.5 m 
C) 5 m 
D) 10 m 
E) 100 m

Question 20

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)

Exam 7: Kinetic Energy and Work

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 crate moves 10 m to the right on a horizontal surface as a woman pulls on it with a 10-N force.Rank the situations shown below according to the work done by her force, least to greatest.

Which of the following five quantities is NOT an expression for energy? Here m is a mass, g is the acceleration due to gravity, h and d are distances, F is a force, v is a speed, a is an acceleration, P is power, and t is time.

A man pushes an 80-N crate a distance of 5.0 m upward along a frictionless slope that makes an angle of 30 °\degree° with the horizontal.The force he exerts is parallel to the slope.If the speed of the crate is constant, then the work done by the man is:

Which of the following five units represents a quantity that is NOT the same type as the other four?

At time t = 0 a particle starts moving along the x axis.If its kinetic energy increases uniformly with t the net force acting on it must be:

Two trailers, X with mass 500 kg and Y with mass 2000 kg, are being pulled at the same speed.The ratio of the kinetic energy of Y to that of X is:

A particle moves 5 m in the positive x direction while being acted upon by a constant force = (4 N)+ (2 N)- (4 N).The work done on the particle by this force is:

Three identical springs (X, Y, Z)are arranged as shown.When a 4.0-kg mass is hung on X, the mass descends 3.0 cm.When a 6.0-kg mass is hung on Y, the mass descends:

When a certain rubber band is stretched a distance x, it exerts a restoring force F = ax + bx2, where a and b are constants.The work done in stretching this rubber band from x = 0 to x = L 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:

An object is constrained by a cord to move in a circular path of radius 0.5m on a horizontal frictionless surface.The cord will break if its tension exceeds 16N.The maximum kinetic energy the object can have is:

An 8-N block slides down an incline.It has an initial speed of 7 m/s.The work done by the resultant force on this block is:

A man moves the 10-g object shown in a vertical plane at a constant speed from position X to position Y along a circular track of radius 20 m.The process takes 0.75 min.The work done by the man is about:

A man pushes an 80-N crate a distance of 5.0 m upward along a frictionless slope that makes an angle of 30 °\degree° with the horizontal.His force is parallel to the slope.If the speed of the crate decreases at a rate of 1.5 m/s2, then the work done by the man is:

When a certain rubber band is stretched a distance x, it exerts a restoring force of magnitude F = Ax, where A is a constant.The work done by a person in stretching this rubber band from x = 0 to x = L is:

One watt is:

A force = (4.1 N)+ (2.6 N)- (4.7 N)acts on a mass of 2.3 kg as it moves in the x direction at a speed of 7.2 m/s.What is the rate at which the force is doing work?

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

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:

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A man pushes an 80-N crate a distance of 5.0 m upward along a frictionless slope that makes an angle of 30 $\degree$ with the horizontal.The force he exerts is parallel to the slope.If the speed of the crate is constant, then the work done by the man is:

When a certain rubber band is stretched a distance x, it exerts a restoring force F = ax + bx², where a and b are constants.The work done in stretching this rubber band from x = 0 to x = L is:

A man pushes an 80-N crate a distance of 5.0 m upward along a frictionless slope that makes an angle of 30 $\degree$ with the horizontal.His force is parallel to the slope.If the speed of the crate decreases at a rate of 1.5 m/s², then the work done by the man is: