Question 1

Use the figure to answer the question. A light rope runs through two frictionless pulleys of negligible mass.A mass,m,is hung from one of the pulleys and a force,F is applied to one end of the rope so that the mass moves at a constant speed. 
-A car and its occupants,with a total mass m,are moving at a speed v relative to an observer on the side of the road.You are driving in another car,also traveling at speed v,and in the same direction as the first car.The kinetic energy of the first car relative to you is

Accepted Answer

A) 0 
B)   mv2 
C)   m(2v)2 
D)   m (3v)2 
E) depends on the mass of your car

Question 2

A body moves with decreasing speed.Which of the following statements is true?

Accepted Answer

A) The net work done on the body is positive,and the kinetic energy is increasing. 
B) The net work done on the body is positive,and the kinetic energy is decreasing. 
C) The net work done on the body is zero,and the kinetic energy is decreasing. 
D) The net work done on the body is negative,and the kinetic energy is increasing. 
E) The net work done on the body is negative,and the kinetic energy is decreasing.

Question 3

Use the figure for the question. The graph shows the speed of a light truck of mass 4000 kg coasting on neutral down a level straight road.The truck is slowing down due to air resistance and rolling friction. 
-Suppose the driver decides to put the truck in gear and steps on the accelerator at 5s.What is the power needed to maintain the speed at 5s?

Accepted Answer

A) 20 kW 
B) 40 kW 
C) 60 kW 
D) 80 kW 
E) 100 kW

Question 4

A bullet with a mass of 12 g moving horizontally strikes a fixed block of wood and penetrates a distance of 5.2 cm.The speed of the bullet just before the collision is 640 m/s.The average force that the wood exerted on the bullet was

Accepted Answer

A) 4.7 $\times$ 104 N 
B) 74 N 
C) 4.7 $\times$ 106 N 
D) unknown; the mass of the wood is required 
E) None of these is correct.

Question 5

The kinetic energy of a car is 1.00 $\times$ 105 J.If the car's speed is increased by 20 percent,the kinetic energy of the car becomes

Accepted Answer

A) 4.00 $\times$ 103 J 
B) 1.20 $\times$ 105 J 
C) 1.44 $\times$ 105 J 
D) 1.04 $\times$ 105 J 
E) unknown; the answer depends on the mass of the car,which is not given

Question 6

An object of mass,m,is placed in an arc of a circle of radius,r.The coefficient of kinetic friction between the object and the surface of the arc is $\mu$k.What is the work done by friction in going from P1 and P2?

Accepted Answer

A) -$\mu$kmg r (cos($\theta$2)-cos($\theta$1)) 
B) -$\mu$kmg r (sin($\theta$2)-sin($\theta$1)) 
C) -$\mu$kmg r cos($\theta$2)sin$\theta$1) 
D) -$\mu$kmg r sin($\theta$2)cos($\theta$1) 
E) none of the above

Question 7

A body is acted upon by a force of 10 N and undergoes a displacement in the direction of the force in accordance with the relation s = 3t2 + 2t,where s is the displacement in meters and t is in seconds.The rate at which the force is doing work at the instant t = 2 s is

Accepted Answer

A) 14 W 
B) 12 W 
C) 120 W 
D) 140 W 
E) 160 W

Question 8

A particle moves halfway around a circle of radius R.It is acted on by a radial force of magnitude F.The work done by the radial force is

Accepted Answer

A) zero 
B) FR 
C) F$\pi$R 
D) 2FR 
E) 2$\pi$R

Question 9

Negative work means

Accepted Answer

A) the kinetic energy of the object increases. 
B) the applied force is variable. 
C) the applied force is perpendicular to the displacement. 
D) the applied force is opposite to the displacement. 
E) nothing; there is no such thing as negative work.

Question 10

The SI unit of energy can be expressed as

Accepted Answer

A) kg · m/s 
B) kg · m/s2  
C) m/(kg · s) 
D) kg · m · s2  
E) None of these is correct.

Question 11

A 5-kg object slides down a frictionless surface inclined at an angle of 30º from the horizontal.The total distance moved by the object along the plane is 10 meters.The work done on the object by the normal force of the surface is

Accepted Answer

A) zero 
B) 0.50 kJ 
C) 0.43 kJ 
D) 0.58 kJ 
E) 0.25 kJ

Question 12

A hydroelectric power plant generates electricity from water falling a height of h m and at a rate of 20,000 kg/s.If the theoretical maximum power output of the plant is 15.0 MW what is the height h?

Accepted Answer

A) 750 m 
B) 153 m 
C) 102 m 
D) 76.5 m 
E) 38.3 m

Question 13

A motor is lifting a mass of 35.0 kg at a constant speed of 6.00 m/s.If friction is neglected,the power developed by the motor to do this lifting is

Accepted Answer

A) 740 W 
B) 1.5 $\times$ 103 W 
C) 2.1 $\times$ 103 W 
D) 59 W 
E) 43 W

Question 14

Use the figure to answer the question. A light rope runs through two frictionless pulleys of negligible mass.A mass,m,is hung from one of the pulleys and a force,F is applied to one end of the rope so that the mass moves at a constant speed. 
-If the force is applied over a distance,d,the distance the mass moves is

Accepted Answer

A) 0 
B)   d 
C)   d 
D) d 
E) 2d

Question 15

As a punishment for being late to a practice session the coach orders her star athlete to run up the stadium steps.The player's mass is 80 kg and it takes one minute for her to run up the 120 steps at a constant rate.If each step is of height 0.5 m,what is the power output of the player?

Accepted Answer

A) 80.0 W 
B) 13.0 W 
C) 1570 W 
D) 785 W 
E) 390 W

Question 16

Initially a body moves in one direction and has kinetic energy K.Then it moves in the opposite direction with three times its initial speed.What is the kinetic energy now?

Accepted Answer

A) K 
B) 3K 
C) -3K 
D) 9K 
E) -9K

Question 17

What is the power output needed from a motor to lift,in the absence of friction,a mass of 1.5 $\times$ 104 kg 25 m in 6.0 s at constant speed?

Accepted Answer

A) 2.0 $\times$ 106 W 
B) 6.1 $\times$ 105 W 
C) 2.2 $\times$ 104 W 
D) 8.3 $\times$ 105 W 
E) 3.1 $\times$ 105 W

Question 18

If a fighter jet doubles its speed,by what factor should the power from the engine change?

Accepted Answer

A) by half 
B) unchanged 
C) doubled 
D) quadrupled 
E) 8 times

Question 19

A constant force of 45 N directed at angle $\theta$ to the horizontal pulls a crate of weight 100 N from one end of a room to another a distance of 4 m.Given that the vertical component of the pulling force is 12 N,calculate the work done by the force in moving the crate.

Accepted Answer

A) 4.1 $\times$ 102 J 
B) 48.0 J 
C) 3.9 $\times$ 102 N/m 
D) 1.7 $\times$ 102 J 
E) 3.9 $\times$ 103 J

Question 20

Power P is required to do work W in time interval t.What power is required to do work 3W in time interval 5t?

Accepted Answer

A) P 
B) 3P 
C) 5P 
D) 5P/3 
E) 3P/5

Exam 6: Work and Energy

A body moves with decreasing speed.Which of the following statements is true?

A bullet with a mass of 12 g moving horizontally strikes a fixed block of wood and penetrates a distance of 5.2 cm.The speed of the bullet just before the collision is 640 m/s.The average force that the wood exerted on the bullet was

The kinetic energy of a car is 1.00 $\times$ 10⁵ J.If the car's speed is increased by 20 percent,the kinetic energy of the car becomes

A body is acted upon by a force of 10 N and undergoes a displacement in the direction of the force in accordance with the relation s = 3t² + 2t,where s is the displacement in meters and t is in seconds.The rate at which the force is doing work at the instant t = 2 s is

A particle moves halfway around a circle of radius R.It is acted on by a radial force of magnitude F.The work done by the radial force is

Negative work means

The SI unit of energy can be expressed as

A 5-kg object slides down a frictionless surface inclined at an angle of 30º from the horizontal.The total distance moved by the object along the plane is 10 meters.The work done on the object by the normal force of the surface is

A hydroelectric power plant generates electricity from water falling a height of h m and at a rate of 20,000 kg/s.If the theoretical maximum power output of the plant is 15.0 MW what is the height h?

A motor is lifting a mass of 35.0 kg at a constant speed of 6.00 m/s.If friction is neglected,the power developed by the motor to do this lifting is

As a punishment for being late to a practice session the coach orders her star athlete to run up the stadium steps.The player's mass is 80 kg and it takes one minute for her to run up the 120 steps at a constant rate.If each step is of height 0.5 m,what is the power output of the player?

Initially a body moves in one direction and has kinetic energy K.Then it moves in the opposite direction with three times its initial speed.What is the kinetic energy now?

What is the power output needed from a motor to lift,in the absence of friction,a mass of 1.5 $\times$ 10⁴ kg 25 m in 6.0 s at constant speed?

If a fighter jet doubles its speed,by what factor should the power from the engine change?

A constant force of 45 N directed at angle $\theta$ to the horizontal pulls a crate of weight 100 N from one end of a room to another a distance of 4 m.Given that the vertical component of the pulling force is 12 N,calculate the work done by the force in moving the crate.

Power P is required to do work W in time interval t.What power is required to do work 3W in time interval 5t?

Exam 6: Work and Energy

A body moves with decreasing speed.Which of the following statements is true?

A bullet with a mass of 12 g moving horizontally strikes a fixed block of wood and penetrates a distance of 5.2 cm.The speed of the bullet just before the collision is 640 m/s.The average force that the wood exerted on the bullet was

The kinetic energy of a car is 1.00 ×\times× 105 J.If the car's speed is increased by 20 percent,the kinetic energy of the car becomes

An object of mass,m,is placed in an arc of a circle of radius,r.The coefficient of kinetic friction between the object and the surface of the arc is μ\muμ k.What is the work done by friction in going from P1 and P2?

A body is acted upon by a force of 10 N and undergoes a displacement in the direction of the force in accordance with the relation s = 3t2 + 2t,where s is the displacement in meters and t is in seconds.The rate at which the force is doing work at the instant t = 2 s is

A particle moves halfway around a circle of radius R.It is acted on by a radial force of magnitude F.The work done by the radial force is

Negative work means

The SI unit of energy can be expressed as

A 5-kg object slides down a frictionless surface inclined at an angle of 30º from the horizontal.The total distance moved by the object along the plane is 10 meters.The work done on the object by the normal force of the surface is

A hydroelectric power plant generates electricity from water falling a height of h m and at a rate of 20,000 kg/s.If the theoretical maximum power output of the plant is 15.0 MW what is the height h?

A motor is lifting a mass of 35.0 kg at a constant speed of 6.00 m/s.If friction is neglected,the power developed by the motor to do this lifting is

As a punishment for being late to a practice session the coach orders her star athlete to run up the stadium steps.The player's mass is 80 kg and it takes one minute for her to run up the 120 steps at a constant rate.If each step is of height 0.5 m,what is the power output of the player?

Initially a body moves in one direction and has kinetic energy K.Then it moves in the opposite direction with three times its initial speed.What is the kinetic energy now?

What is the power output needed from a motor to lift,in the absence of friction,a mass of 1.5 ×\times× 104 kg 25 m in 6.0 s at constant speed?

If a fighter jet doubles its speed,by what factor should the power from the engine change?

A constant force of 45 N directed at angle θ\thetaθ to the horizontal pulls a crate of weight 100 N from one end of a room to another a distance of 4 m.Given that the vertical component of the pulling force is 12 N,calculate the work done by the force in moving the crate.

Power P is required to do work W in time interval t.What power is required to do work 3W in time interval 5t?

The kinetic energy of a car is 1.00 $\times$ 10⁵ J.If the car's speed is increased by 20 percent,the kinetic energy of the car becomes

A body is acted upon by a force of 10 N and undergoes a displacement in the direction of the force in accordance with the relation s = 3t² + 2t,where s is the displacement in meters and t is in seconds.The rate at which the force is doing work at the instant t = 2 s is

What is the power output needed from a motor to lift,in the absence of friction,a mass of 1.5 $\times$ 10⁴ kg 25 m in 6.0 s at constant speed?

A constant force of 45 N directed at angle $\theta$ to the horizontal pulls a crate of weight 100 N from one end of a room to another a distance of 4 m.Given that the vertical component of the pulling force is 12 N,calculate the work done by the force in moving the crate.