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College Physics - PH 201 > Chapter 7: Introduction to Work, Energy, and Energy Resources > Flashcards

Chapter 7: Introduction to Work, Energy, and Energy Resources Flashcards

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1
Q

Define basal metabolic rate

A

the total energy conversion rate of a person at rest

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1
Q

Define chemical energy

A

the energy in a substance stored in the bonds between atoms and molecules that can be released in a chemical reaction

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2
Q

Define the conservation of mechanical energy.

A

the rule that the sum of the kinetic energies and potential energies remains constant if only conservative forces act on and within a system

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3
Q

Define conservative force

A

a force that does the same work for any given initial and final configuration, regardless of the path followed

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4
Q

Define efficiency

A

a measure of the effectiveness of the input of energy to do work; useful energy or work divided by the total input of energy

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5
Q

Define electrical energy

A

the energy carried by a flow of charge

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6
Q

Define energy

A

the ability to do work

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7
Q

Define fossil fuels

A

Oil, natural gas, coal, etc.

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8
Q

Define friction

A

the force between surfaces that opposes one sliding on the other; friction changes mechanical energy into thermal energy

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9
Q

Define gravitational potential energy

A

the energy an object has due to its position in a gravitational field

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10
Q

Define horsepower

A

An older non-SI unit of power, with 1hp = 746 W

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11
Q

Define kilowatt-hour

A

unit used primarily for electrical energy provided by electric utility companies (KWh)

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12
Q

Define kinetic energy:

A

the energy an object has by reason of its motion, equal to1/2mv^2for the translational (i.e., non-rotational) motion of an object of massm moving at speedv

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13
Q

Define law of conservation of energy

A

the general law that total energy is constant in any process; energy may change in form or be transferred from one system to another, but the total remains the same

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14
Q

Define mechanical energy

A

the sum of kinetic energy and potential energy

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15
Q

Define metabolic rate

A

the rate at which the body uses food energy to sustain life and to do different activities

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16
Q

Define net work

A

work done by the net force, or vector sum of all the forces, acting on an object

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17
Q

Define nonconservative force

A

a force whose work depends on the path followed between the given initial and final configurations

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18
Q

Define nuclear energy

A

energy released by changes within atomic nuclei, such as the fusion of two light nuclei or the fission of a heavy nucleus

19
Q

Define potential energy

A

energy due to position, shape, or configuration

20
Q

Define the potential energy of a spring.

A

the stored energy of a spring as a function of its displacement; when Hooke’s law applies, it is given by the expression1/2kx^2wherex is the distance the spring is compressed or extended andk is the spring constant

21
Q

Define power

A

The rate at which work is done

22
Q

Define radiant energy

A

the energy carried by electromagnetic waves

23
Q

Define thermal energy

A

the energy within an object due to the random motion of its atoms and molecules that accounts for the object’s temperature

24
Q

Define useful work

A

Work done on an external system

25
Q

Define Watt

A

SI unit of power, with1 W=1 J/s

26
Q

Define work

A

the transfer of energy by a force that causes an object to be displaced; the product of the component of the force in the direction of the displacement and the magnitude of the displacement

27
Q

Define work-energy theorem

A

the result, based on Newton’s laws, that the net work done on an object is equal to its change in kinetic energy

28
Q

What is the formula for work?

A

W = Fdcosθ

W = work
F = force
d = displacement
cosθ = cos of the angle between f and d

29
Q

What is the equation for kinetic energy?

A

KE = 1/2 m v^2

30
Q

What is the work-energy theorem equation?

A

Wnet = 1/2mv^2 - 1/2mv_o^2

Wnet = net work
m = mass
v = velocity
v_o = initial velocity

31
Q

What is the equation for the change in gravitational potential energy?

A

ΔPEg=mgh

ΔPEg = change in gravitational of potential energy
m = mass
g = gravity
h = height

32
Q

How do KE (kinetic energy) and PE (potential energy) relate to each other?

A

ΔKE= −ΔPEg

33
Q

What is the formula for the potential energy of a spring?

A

PEs = 1/2 kx^2

PEs = potential energy of spring
k = spring constant
x = displacement

34
Q

What is the formula for mechanical energy?

A

KE + PE
or
KEi = PEi = KEf + PEf

35
Q

What does the law of conservation of energy state?

A

the total energy is constant in any process. Energy may change in form or be transferred from one system to another, but the total remains the same.

36
Q

When all forms of energy are considered, how is the conservation of energy written in equation form?

A

KEi+PEi+Wnc+OEi=KEf+PEf+OEf

KEi = inital kinetic energy
PEi = inital potential energy
Wnc = word done by non-conservative energy
OEi = initial other forms of energy

vice versa

37
Q

How to calculate efficiency?

A

Eff = Wout / Ein

Eff = efficiency
Wout = useful work output
Ein = energy consumed

38
Q

What is the equation for power?

A

P = W/t

P = power
W = work
t = time

39
Q

What is power’s unit?

A

Watt (W)

40
Q

Magnus has reached the finals of a strength competition. IN the first round, he has to pull a city bus as far as he can. One end of a rope is attached to the bus and the other is tied around Magnus’s waist. If a force gauge placed halfway down the rope reads out a constant 2100 Newtons while Magnus pulls the bus a distance of 1.05 meters, how much work does the tension force do on Magnus? The rope is perfectly horizontal during the pull.

A

-2205 J

Explanation:

I. Assess what you have: force and distance

II. Assess what you need: work

III. Find the right equation: W = +/- Fd

IV. plug in the numbers: W = -(2100N)(1.05m)
a. negative because it’s frictional

V. Solve: W = -2205 J
a. J = N/m

41
Q

A ball of mass 0.600kg is carefully balanced on a shelf that is 2.30 m above the ground. What is its gravitational potential energy?

A

13.5 J

Explanation:

PE = mgh

PE = (0.600kg)(9.81m/s^2)(2.3m)

PE = 13.5J

42
Q

A boy swings a ball on a string at constant speed in a circle that has a circumference equal to 6m

What is the work done on the ball by the 10 N tension force in the strong during one revolution of the ball?

A

0 J

Explanation: Centripetal force is always perpendicular to velocity. Perpendicular would give us cos90 which is equal to 0

43
Q

A ball of mass 0.600 kg fell from a shelf 2.3 m off the ground with a potential energy of 13.5J (before falling). How fast will the ball be moving just before it strikes the ground?

A

6.71m/s

Explanation:

KE = 1/2mv^2

Get velocity to one side

v = sqrt 2KE / m

Plug in numbers and solve

v = sqrt 2 * 13.5J / 0.600

V = 6.71m/s

44
Q

What is the work-energy theorem regarding kinetic energy?

A

Wnet = KE - KEo

College Physics - PH 201 (10 decks)

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