Deck 5: Energy

Question 1

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.

Answer 1

friction

Question 2

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

Answer 2

108 J

Question 3

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

Answer 3

125 J

Question 4

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 5

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 6

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

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

Question 7

A student has to work the following problem: A block is being pulled along at constant speed on a horizontal surface a distance d by a rope supplying a force F at an angle of elevation q.The surface has a frictional force acting during this motion.How much work was done by friction during this motion? The student calculates the value to be -Fdsinq.How does this value compare to the correct value?

A)It is the correct value.
B)It is too high.
C)It is too low.
D)The answer cannot be found until it is known whether q is greater than,less than,or equal to 45 $\degree$ .

Question 8

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 9

The work done by static friction can be:

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

Question 10

A 50.0-kg (including the passenger)sled is subject to a net force of 20.0 N pushing in the direction of the sled's motion as it is moving over a horizontal surface for a distance of 11.0 m after having started from rest.At this point the sled is released as it starts down a 10.0 $\degree$ incline.However,the snow is not very deep,and the sled stops after having moved an additional 35.0 m.What is the work done by friction while the sled is on the incline?

A)-220 J
B)-3200 J
C)-858 J
D)-2980 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

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 13

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

Question 14

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 15

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 16

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)It decreases.
B)It increases.
C)It remains constant.
D)It cannot be determined from the information given.

Question 17

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 18

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 19

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 20

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 21

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 22

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 23

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 24

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 25

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 26

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 27

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 28

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 29

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 30

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 31

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 32

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 33

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 34

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 35

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 36

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 37

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 38

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 39

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 40

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 41

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 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

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 44

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 45

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 46

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 47

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 48

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 49

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 50

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 51

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 52

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 53

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 54

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 55

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 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 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 58

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 59

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 60

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 61

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 62

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 63

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 64

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 65

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 66

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 67

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 68

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 69

The area under the force vs.displacement curve represents:

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

Question 70

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

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

Question 71

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 72

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 73

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 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 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 76

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 77

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 78

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 79

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 80

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.