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Energy Unit Student Design Cover Page

(See directions on page 19)

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Energy Unit Front Page

At the end of this unit I will be able to:

q Define and describe work. q Describe the role of energy in

physical processes and living organisms.

q Complete calculations of power, energy, force, and work.

q Differentiate between potential energy and kinetic energy.

q Use the law of conservation of energy to predict kinetic energy, potential energy, or velocity.

Quantities and units I will understand and use are:q Quantities: Work, power, mechanical energy, kinetic energy, force, mass, velocity, distanceq Units: Joule, watt, newton, kilogram, m/s (meters per second), meters

The terms I will clearly define are:q Efficiency, energy, fulcrum, joule, kinetic energy, law of conservation of energy, lever,

machine, mechanical advantage, mechanical energy, potential energy, power, pulley, watt, work, work-energy theorem

The assignments I will have completed by the end of the unit are:q

q

q

q

q

q

q

q

q

q

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Energy Unit Formulas, Quantities, and Units

W = F dVariables in equation: Units for variable: Misc. info

W = (J) 1 joule = 1 N 1 m

F = (N)

d = _ (m)

P = W t

Variables in equation: Units for variable: Misc. info

P = (W)* 1 watt = 1 joule/sec

W* = (J)

t = (s)

*Be careful!

GPE = mgh

Variables in equation: Units for variable: Misc. info

GPE =(J)

m = (kg)

g = (m/s2)

h = (m)

KE = ½mv2

Variables in equation:

Units for variable: Misc. info

KE = (J)

m = (kg)

v = (m/s)

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Checking for Understanding: Work & Power

1. Compared to lifting one book, how much more work is done when lifting two books the same distance?

2. Compared to lifting one book, how much more work is done when lifting two books twice as far?

3. Which requires more work, lifting a 10-kg load a vertical distance of 2 m or lifting a 5-kg load a vertical distance of 4 m?

4. How much power is required to do 100 J of work on an object in a time of 0.5 sec?

5. How much power is required to do 100 J of work on an object in a time of 1.0 sec?

6. Explain how work and impulse are similar and different. Write at least 3 complete sentences. Include the units for both quantities in your explanation.

7. Two elevators do the same job of lifting 10 identical passengers up three floors, yet the machines have different power outputs. How is this possible?

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Work & Power Notes

What is work?

Work is done when _______________________________________________________________________________________________________________________________________________

W =

What is the unit for work?

Work is measured in _________________________________(J).

1 J = ________________________________________________________

Is holding a heavy book considered work?

Work is done ________________________________________:

o A force is applied

o _______________________________________________________

_______________________________________________________

If you _________________________________ you are ________________________

__________________________________________________________________________

The work that is done is on __________________________________________

__________________________________________________________________________

What is power?

Power is __________________________________________________________________________

_____________________________________________________________________________________

P =

Power is measured in __________________________________

1 watt =

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Simple Power/Work Calculations:

1. Calculate the work done when a 20-N force pushes a cart 3.5 m.

2. Calculate the work done in lifting a 500-N barbell 2.2 m above the floor.

3. Calculate the power expended when the barbell above is lifted 2.2 m in 2 s.

4. What work is done in lifting a 50-kg block to a height of 20 m?

5. What is the work done in raising a 20-kg package 60 cm vertically?

6. Determine the power expended when a barbell is raised 4.0 m in 2 seconds.

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Warm Up:

Jack and Jill ran up the hill. Jack is twice as massive as Jill; yet Jill ascended the same distance in half the time.

a. Who did the most work? Use the space below to write out any relevant formulas and to brainstorm, then answer the question at the bottom in well thought-out, complete sentences!

b. Who delivered the most power? Use the space below to write out any relevant formulas and to brainstorm, then answer the question at the bottom in well thought-out, complete sentences!

Calculating Power and Work

1. A person lifts a package weighing 75 N. If she lifts it 1.2 m off the floor, what work has she done?

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2. When 142 J of work is done in pushing a box horizontally 13.3 m, how much force is applied?

3. What work is done when a person pushes a refrigerator weighing 720 N across a floor 12 m if the force of friction between the refrigerator and the floor is 480 N?

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Calculating Power and Work

4. A student applies an upward force to lift a 129-kg barbell to a height of 1.98 m at a constant speed. How much work is done?

5. On a recent adventure trip, Anita Break went rock-climbing. Anita was able to steadily lift her 80.0-kg body 20.0 meters in 100 seconds. Determine Anita’s power rating during this portion of the climb.

6.

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Forms of Energy

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Energy Notes

What is mechanical energy

and what are the two

types?

Mechanical Energy (ME) is energy that ___________________________________

______________________________________________

Two types of mechanical energy:

1. ________________________________________________(PE) -- The energy

due to an object’s _______________________________

2. ________________________________________________ (KE) -- The energy

due to an object’s ________________________________

Energy is measured in ____________________

What is potential energy?

Potential energy is energy that has _______________________________

_________________________________________.

The energy is considered in a __________________________________.

__________________________________________________ in fuels, electric

batteries, and the food we eat is potential energy due to the

positions of the electrical charges at a submicroscopic level!

What is gravitational

potential energy?

To elevate an object, ___________________ must be done to lift the

object against ___________________________________________________.

How much work must be done to elevate the object is also the

amount of PE it has!

Gravitational potential energy is the energy ____________________

____________________________________________________

GPE =

GPE =

GPE =

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Energy Notes

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Energy Notes

What is kinetic energy?

• If an object is moving, it can _____ _________________!

• Kinetic energy is the ________________________________________, and

depends on the ____________________________________________________.

• KE =

• KE = Work required ______________________________________________

______________________________________________________________________

• KE =

• ½ mv2 =

Explain the law of

conservation of energy.

• Whenever work is done, _______________________________________.

Law of conservation of energy:

_______________________________________________________________________________

_______________________________________________________________________________

• ME = KE + PE

• The total ______________ is conserved, even if ___________ and

___________ change.

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Potential Energy & Kinetic Energy Venn Diagram

Warm Up:

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Checking for Understanding: Energy

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Energy Unit Study Guide

1. Circle “yes” or “no” to indicate whether work was done in each situation below. Then, explain your answer.

a. A teacher applies a force to a wall and becomes exhausted.Explanation: Yes or No?

b. A weightlifter lifts a barbell above her head.Explanation: Yes or No?

c. A waiter carries a tray full of meals across a dining room at a constant speed. Explanation: Yes or No?

d. A rolling marble hits a note card and moves it across a table. Explanation: Yes or No?

e. A shot-putter launches the shot.Explanation: Yes or No?

2. Two physics students are in the weightlifting room. Will lifts the 100-pound barbell over his head 10 times in one minute; Ben lifts the 100-pound barbell over his head 10 times in 10 seconds.

a. Which student does the most work?

b. Which student delivers the most power?

3. Bart runs up a 2.91-meter high flight of stairs at a constant speed in 2.15 seconds. If Bart’s mass is 65.9 kg, determine the work which he did and his power rating.

4.

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Energy Unit Concept Map(see page 19 for directions)

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Energy Unit Concept Cards

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Energy Unit Back Page

The California Dept. of Education Standards I have come to understand are:

q 2.a. Students know how to calculate kinetic energy by using the formula E = (1/2)mv2.

q 2.b. Students know how to calculate changes in gravitational potential energy near Earth by

using the formula (change in potential energy) =mgh (h is the change in the elevation).

q 2.e. Students know momentum is a separately conserved quantity different from energy.

q 2.g. Students know how to solve problems involving elastic and inelastic collisions in one

dimension by using the principles of conservation of momentum and energy.

q 3.a. Students know heat flow and work are two forms of energy transfer between systems.

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