Deck 5: Energy

Question 1

The unit of work, joule, is dimensionally the same as:

A)newton/second.
B)newton/kilogram.
C)newton-second.
D)newton-meter.

Answer 1

newton-meter.

Question 2

A horizontal force of 100 N is applied to move a 45-kg cart across a 9.0-m level surface.What work is done by the 100-N force?

A)405 J
B)500 J
C)900 J
D)4 500 J

Answer 2

900 J

Question 3

If during a given physical process the only force acting on an object is friction, which of the following must be assumed in regard to the object's kinetic energy?

A)decreases
B)increases
C)remains constant
D)cannot tell from the information given

Answer 3

cannot tell from the information given

Question 4

Which of the following is an example of a nonconservative force?

A)gravity
B)magnetism
C)friction
D)Both choices A and B are valid.

Question 5

Which of the following is that form of energy associated with an object's location in a conservative force field?

A)potential
B)thermal
C)bio-chemical
D)kinetic

Question 6

A very light cart holding a 300-N box is moved at constant velocity across a 15-m level surface.What is the net work done in the process?

A)zero
B)1/20 J
C)20 J
D)2 000 J

Question 7

A golf ball hits a wall and bounces back at 3/4 the original speed.What part of the original kinetic energy of the ball did it lose in the collision?

A)1/4
B)3/8
C)7/16
D)9/16

Question 8

What is the kinetic energy of a 0.135-kg baseball thrown at 40.0 m/s (90.0 mph)?

A)54.0 J
B)87.0 J
C)108 J
D)216 J

Question 9

A horizontal force of 200 N is applied to a 55-kg cart across a 10-m level surface.If the cart accelerates at 2.0 m/s², then what is the work done by the force of friction as it acts to retard the motion of the cart?

A)-1 100 J
B)-900 J
C)-800 J
D)-700 J

Question 10

Rupel pushes a box 5.00 m by applying a 25.0-N horizontal force.What work does she do?

A)10.0 J
B)25.0 J
C)125 J
D)550 J

Question 11

A satellite is held in orbit by a 2 000-N gravitational force.Each time the satellite completes an orbit of circumference 80 000 km, the work done on it by gravity is:

A)1.6 * 10⁸ J.
B)1.6 * 10¹¹ J.
C)6.4 * 10¹¹ J.
D)0.

Question 12

If both mass and velocity of a ball are tripled, the kinetic energy is increased by a factor of:

A)3.
B)6.
C)9.
D)27.

Question 13

A rock is thrown straight up with an initial velocity of 15.0 m/s.Ignore energy lost to air friction.How high will the rock rise?

A)1.53 m
B)22.9 m
C)6.50 m
D)11.5 m

Question 14

The work done by static friction can be:

A)positive.
B)negative.
C)zero.
D)Any of the above.

Question 15

What is the minimum amount of energy required for an 80-kg climber carrying a 20-kg pack to climb Mt.Everest, 8 850 m high?

A)8.67 MJ
B)4.16 MJ
C)2.47 MJ
D)1.00 MJ

Question 16

I use a rope 2.00 m long to swing a 10.0-kg weight around my head.The tension in the rope is 20.0 N.In half a revolution how much work is done by the rope on the weight?

A)40.0 J
B)126 J
C)251 J
D)0

Question 17

A 1 200-kg automobile moving at 25 m/s has the brakes applied with a deceleration of 8.0 m/s².How far does the car travel before it stops?

A)39 m
B)47 m
C)55 m
D)63 m

Question 18

A worker pushes a sled with a force of 40 N over a level distance of 6.0 m.If a frictional force of 24 N acts on the wheelbarrow in a direction opposite to that of the worker, what net work is done on the wheelbarrow?

A)240 J
B)216 J
C)144 J
D)96 J

Question 19

Which of the following is that form of energy associated with an object's motion?

A)potential
B)thermal
C)bio-chemical
D)kinetic

Question 20

A 7.00-kg bowling ball falls from a 2.00-m shelf.Just before hitting the floor, what will be its kinetic energy? (g = 9.80 m/s² and assume air resistance is negligible)

A)14.0 J
B)19.6 J
C)29.4 J
D)137 J

Question 21

Samantha pushes a 50-N crate up a ramp 25.0 m in length and inclined at 10 $\degree$ with the horizontal.What potential energy change does the crate experience?

A)13 J
B)55 J
C)120 J
D)220 J

Question 22

A 2.00-kg ball has zero kinetic and potential energy.Ernie drops the ball into a 10.0-m-deep well.Just before the ball hits the bottom, the sum of its kinetic and potential energy is:

A)zero.
B)196 J.
C)-196 J.
D)392 J.

Question 23

A simple pendulum, 1.00 m in length, is released from rest when the support string is at an angle of 35.0 $\degree$ from the vertical.What is the speed of the suspended mass at the bottom of the swing? (g = 9.80 m/s² and ignore air resistance)

A)0.67 m/s
B)0.94 m/s
C)1.33 m/s
D)1.88 m/s

Question 24

An 80 000-kg airliner is flying at 900 km/h at a height of 10.0 km.What is its total energy (kinetic + potential) if the total was 0 when the airliner was at rest on the ground?

A)250 MJ
B)478 MJ
C)773 MJ
D)10 300 MJ

Question 25

A baseball outfielder throws a baseball of mass 0.15 kg at a speed of 40 m/s and initial angle of 30 $\degree$ .What is the kinetic energy of the baseball at the highest point of the trajectory? Ignore air friction.

A)zero
B)30 J
C)90 J
D)120 J

Question 26

A professional skier reaches a speed of 56 m/s on a 30 $\degree$ ski slope.Ignoring friction, what was the minimum distance along the slope the skier would have had to travel, starting from rest?

A)110 m
B)160 m
C)320 m
D)640 m

Question 27

A 2.00-kg ball has zero potential and kinetic energy.Maria drops the ball into a 10.0-m-deep well.After the ball comes to a stop in the mud, the sum of its potential and kinetic energy is:

A)zero.
B)196 J.
C)-196 J.
D)392 J.

Question 28

A simple pendulum, 2.0 m in length, is released with a push when the support string is at an angle of 25 $\degree$ from the vertical.If the initial speed of the suspended mass is 1.2 m/s when at the release point, what is its speed at the bottom of the swing? (g = 9.8 m/s²)

A)2.3 m/s
B)2.6 m/s
C)2.0 m/s
D)0.5 m/s

Question 29

A 15.0-kg crate, initially at rest, slides down a ramp 2.0 m long and inclined at an angle of 20 $\degree$ with the horizontal.If there is no friction between ramp surface and crate, what is the kinetic energy of the crate at the bottom of the ramp? (g = 9.8 m/s²)

A)220 J
B)690 J
C)10 J
D)100 J

Question 30

Old Faithful geyser in Yellowstone Park shoots water hourly to a height of 40 m.With what velocity does the water leave the ground?

A)7.0 m/s
B)14 m/s
C)20 m/s
D)28 m/s

Question 31

A bobsled makes a run down an ice track starting at 150 m vertical distance up the hill.If there is no friction, what is the velocity at the bottom of the hill?

A)27 m/s
B)36 m/s
C)45 m/s
D)54 m/s

Question 32

A baseball catcher puts on an exhibition by catching a 0.15-kg ball dropped from a helicopter at a height of 101 m.What is the speed of the ball just before it hits the catcher's glove 1.0 m above the ground? (g = 9.8 m/s² and ignore air resistance)

A)44 m/s
B)38 m/s
C)31 m/s
D)22 m/s

Question 33

A hill is 100 m long and makes an angle of 12 $\degree$ with the horizontal.As a 50-kg jogger runs up the hill, how much work does gravity do on the jogger?

A)49 000 J
B)10 000 J
C)-10 000 J
D)zero

Question 34

When an object is dropped from a tower, what is the effect of the air resistance as it falls?

A)does positive work
B)increases the object's kinetic energy
C)increases the object's potential energy
D)None of the above choices are valid.

Question 35

A 10.0-kg box starts at rest and slides 3.5 m down a ramp inclined at an angle of 10 $\degree$ with the horizontal.If there is no friction between the ramp surface and crate, what is the velocity of the crate at the bottom of the ramp? (g = 9.8 m/s²)

A)6.1 m/s
B)3.5 m/s
C)10.7 m/s
D)8.3 m/s

Question 36

Two blocks are released from the top of a building.One falls straight down while the other slides down a smooth ramp.If all friction is ignored, which one is moving faster when it reaches the bottom?

A)The block that went straight down.
B)The block that went down the ramp.
C)They both will have the same speed.
D)Insufficient information to work the problem.

Question 37

A pole vaulter clears 6.00 m.With what speed does he strike the mat in the landing area?

A)2.70 m/s
B)5.40 m/s
C)10.8 m/s
D)21.6 m/s

Question 38

A 2 000-kg ore car rolls 50.0 m down a frictionless 10.0 $\degree$ incline.If there is a horizontal spring at the end of the incline, what spring constant is required to stop the ore car in a distance of 1.00 m?

A)340 kN/m
B)681 kN/m
C)980 kN/m
D)1 960 kN/m

Question 39

A simple pendulum, 2.0 m in length, is released by a push when the support string is at an angle of 25 $\degree$ from the vertical.If the initial speed of the suspended mass is 1.2 m/s when at the release point, to what maximum angle will it move in the second half of its swing?

A)37 $\degree$
B)30 $\degree$
C)27 $\degree$
D)21 $\degree$

Question 40

As an object is lowered into a deep hole in the surface of the earth, which of the following must be assumed in regard to its potential energy?

A)increase
B)decrease
C)remain constant
D)cannot tell from the information given

Question 41

A girl and her bicycle have a total mass of 40 kg.At the top of the hill her speed is 5.0 m/s.The hill is 10 m high and 100 m long.If the force of friction as she rides down the hill is 20 N, what is her speed at the bottom?

A)5.0 m/s
B)10 m/s
C)11 m/s
D)She stops before she reaches the bottom.

Question 42

A 50-N crate is pulled up a 5-m inclined plane by a worker at constant velocity.If the plane is inclined at an angle of 37 $\degree$ to the horizontal and there exists a constant frictional force of 10 N between the crate and the surface, what is the force applied by the worker?

A)zero
B)20 N
C)30 N
D)40 N

Question 43

A pile driver drives a post into the ground.The mass of the pile driver is 2 500 kg and it is dropped through a height of 8.0 m on each stroke.If the resisting force of the ground is 4.0 * 10⁶ N, how far is the post driven in on each stroke?

A)4.9 cm
B)9.8 cm
C)16 cm
D)49 cm

Question 44

A baseball catcher puts on an exhibition by catching a 0.150-kg ball dropped from a helicopter at a height of 100 m above the catcher.If the catcher "gives" with the ball for a distance of 0.750 m while catching it, what average force is exerted on the mitt by the ball? (g = 9.80 m/s²)

A)78 N
B)119 N
C)197 N
D)392 N

Question 45

A Hooke's law spring is compressed 12.0 cm from equilibrium and the potential energy stored is 72.0 J.What is the spring constant in this case?

A)10 000 N/m
B)5 000 N/m
C)1 200 N/m
D)No answer is correct.

Question 46

A parachutist of mass 50.0 kg jumps out of an airplane at a height of 1 000 m.The parachute deploys, and she lands on the ground with a speed of 5.0 m/s.How much energy was lost to air friction during this jump?

A)49 400 J
B)98 700 J
C)198 000 J
D)489 000 J

Question 47

I drop a 60-g golf ball from 2.0 m high.It rebounds to 1.5 m.How much energy is lost?

A)0.29 J
B)0.50 J
C)0.88 J
D)1.0 J

Question 48

An amount of work equal to 1.5 J is required to compress the spring in a spring-gun.What is the "launch speed" of a 15-g marble?

A)14 m/s
B)15 m/s
C)18 m/s
D)21 m/s

Question 49

A Hooke's law spring is compressed a distance d and is used to launch a particle of mass m vertically to a height h above its starting position.Under double the compression, the spring is now used to launch a particle of mass 2 m.How high does the second mass rise above its starting position?

A)h
B)2 h
C)3 h
D)4 h

Question 50

Adisa pulls a 40-N crate up a 5.0-m long inclined plane at a constant velocity.If the plane is inclined at an angle of 37 $\degree$ to the horizontal and there is a constant force of friction of 10 N between the crate and the surface, what is the net change in potential energy of the crate?

A)120 J
B)-120 J
C)200 J
D)-200 J

Question 51

Preston pushes a wheelbarrow weighing 500 N to the top of a 50.0-m ramp, inclined at 20.0 $\degree$ with the horizontal, and leaves it.Tamara accidentally bumps the wheelbarrow.It slides back down the ramp, during which an 80.0-N frictional force acts on it over the 50.0 m.What is the wheelbarrow's kinetic energy at the bottom at of the ramp? (g = 9.8 m/s²)

A)4 550 J
B)6 550 J
C)8 150 J
D)13 100 J

Question 52

A 20-N crate starting at rest slides down a rough 5.0-m long ramp, inclined at 25 $\degree$ with the horizontal.20 J of energy is lost to friction.What will be the speed of the crate at the bottom of the incline?

A)0.98 m/s
B)1.9 m/s
C)3.2 m/s
D)4.7 m/s

Question 53

The SI units for k, the spring constant, are equivalent to:

A)J.
B)J / N.
C)kg / s².
D)None of the above.

Question 54

A Hooke's law spring is compressed 12.0 cm from equilibrium, and the potential energy stored is 72.0 J.What compression (as measured from equilibrium) would result in 100 J being stored in this case?

A)16.7 cm
B)14.1 cm
C)13.6 cm
D)No answer is correct.

Question 55

A Hooke's law spring is mounted horizontally over a frictionless surface.The spring is then compressed a distance d and is used to launch a mass m along the frictionless surface.What compression of the spring would result in the mass attaining double the kinetic energy received in the above situation?

A)1.41 d
B)1.73 d
C)2.00 d
D)4.00 d

Question 56

A Hooke's law spring is compressed a distance d and is used to launch a mass m vertically to a height h above its starting position.Under the same compression d, the spring is now used to launch a mass of 2m.How high does this second mass rise?

A)h
B)h/2
C)h/1.41
D)h/4

Question 57

A Hooke's law spring is compressed a distance d and is used to launch a mass m vertically to a height h above its starting position.Under double the compression, the spring is now used to launch the mass.How high does the mass now rise above its starting position?

A)2 h
B)1.41 h
C)3 h
D)4 h

Question 58

A Hooke's law spring is mounted horizontally over a frictionless surface.The spring is then compressed a distance d and is used to launch a mass m along the frictionless surface.What compression of the spring would result in the mass attaining double the speed received in the above situation?

A)1.41 d
B)1.73 d
C)2.00 d
D)4.00 d

Question 59

By how much is the energy stored in a Hooke's law spring increased when its stretch is increased from 8.00 cm to 16.0 cm?

A)100%
B)200%
C)300 %
D)The correct answer is not given.

Question 60

A girl and her bicycle have a total mass of 40.0 kg.At the top of the hill her speed is 5.0 m/s, and her speed doubles as she rides down the hill.The hill is 10.0 m high and 100 m long.How much kinetic energy and potential energy is lost to friction?

A)2 420 J
B)1 500 J
C)2 000 J
D)3 920 J

Question 61

A force of 100 N is applied to a 50-kg mass in the direction of motion for a distance of 6.0 m and then the force is increased to 150 N for the next 4.0 m.For the 10 m of travel, how much work is done by the varying force?

A)1 200 J
B)1 500 J
C)2 400 J
D)-1 500 J

Question 62

The unit of power, watt, is dimensionally the same as:

A)joule-second.
B)joule/second.
C)joule-meter.
D)joule/meter.

Question 63

Water flows over a section of Niagara Falls at a rate of 1.20 * 10⁶ kg/s and falls 50.0 m.What is the power dissipated by the waterfall?

A)588 MW
B)294 MW
C)147 MW
D)60.0 MW

Question 64

The net force acting on a 6.0-kg object is given by F_x = (10 - x) N, where F_x is in newtons and x is in meters.How much work is done on the object as it moves from x = 0 to x = 10 m?

A)100 J
B)75 J
C)50 J
D)25 J

Question 65

The net force acting on a 12.6-kg object is given by F_x = (20 - x) N, where F_x is in newtons and x is in meters.How much work is done on the object as it moves from x = 0 to x = 10 m?

A)300 J
B)200 J
C)150 J
D)100 J

Question 66

A 100-W light bulb is left on for 10.0 hours.Over this period of time, how much energy was used by the bulb?

A)1 000 J
B)3 600 J
C)3 600 000 J
D)1.34 hp

Question 67

Is it possible for the total mechanical energy of a moving particle to be negative?

A)No, because a moving particle has positive kinetic energy.
B)No, because potential energy cannot have a value more negative than the value of the positive kinetic energy of the particle.
C)Only if friction is involved.
D)yes

Question 68

The rate at which work is done is equivalent to which of the following?

A)increase in potential energy
B)thermal energy
C)potential energy
D)power

Question 69

A jet engine develops 1.0 * 10⁵ N of thrust in moving an airplane forward at a speed of 900 km/h.What is the power developed by the engine?

A)500 kW
B)10 MW
C)25 MW
D)50 MW

Question 70

A 60-kg woman runs up a flight of stairs having a rise of 4.0 m in a time of 4.2 s.What average power did she supply?

A)380 W
B)560 W
C)620 W
D)670 W

Question 71

A 200-hp engine can deliver, in SI units, an average power of ____.(1 hp = 746 W)

A)200 W
B)74 600 W
C)149 000 W
D)298 000 W

Question 72

The area under the force vs.displacement curve represents:

A)area.
B)force.
C)work.
D)coefficient of static friction.

Question 73

The quantity of work equal to one joule is also equivalent to which of the following?

A)watt
B)watt /s
C)watt * s
D)watt /s²

Question 74

Yuri, a Russian weightlifter, is able to lift 250 kg 2.00 m in 2.00 s.What is his power output?

A)500 W
B)2.45 kW
C)4.90 kW
D)9.80 kW

Question 75

A force of 5.0 N is applied to a 20-kg mass on a horizontal frictionless surface.As the speed of the mass increases at a constant acceleration, the power delivered to it by the force:

A)remains the same.
B)increases.
C)decreases.
D)doubles every 4.0 seconds.

Question 76

A speed boat requires 80 kW to move at a constant speed of 15 m/s.What is the resistive force of the water at this speed?

A)2 700 N
B)5 300 N
C)6 500 N
D)7 700 N

Question 77

A 1 000-kg sports car accelerates from zero to 25 m/s in 7.5 s.What is the average power delivered by the automobile engine?

A)20.8 kW
B)30.3 kW
C)41.7 kW
D)52.4 kW

Question 78

Three different mass projectiles are launched from the top of a building each at different angles of elevation.Each particle has the same initial kinetic energy.Which particle has the greatest speed just as it impacts with the ground?

A)The one launched at the highest angle of elevation.
B)The one with the highest mass.
C)The one with the lowest mass.
D)They all will have the same speed on impact.

Question 79

An automobile delivers 30.0 hp to its wheels when moving at a constant speed of 22.0 m/s.What is the resistance force on the automobile at this speed? (1 hp = 746 watts)

A)18 600 N
B)410 000 N
C)1 020 N
D)848 N

Question 80

Three different mass projectiles are launched from the top of a building each at different angles of elevation.Each particle has the same initial kinetic energy.Which particle has the greatest kinetic energy just as it impacts with the ground?

A)The one launched at the highest angle of elevation.
B)The one with the highest mass.
C)The one with the lowest mass.
D)They all will have the same kinetic energy on impact.