What is Energy? - Central Bucks School District · What is energy? 2. What are some things you have...

1. What is energy? 2. What are some things you

have tried with your racer that are working well?

3. What are some changes you would like to make to your car?

Chapter 5 Section 1

Energy is the ability to do work Work is the transfer of energy ◦ Force moves an object (in the direction of the force)

Measured in Joules (J)

What are some things that make a job feel like

more work?

Decide whether each of the following is work or not…be able to explain your answers. ◦ Pulling a wheeled suitcase

◦ Carrying a suitcase

◦ Picking up a bag of groceries

◦ Carrying a bag of groceries

1. Put your name, date and class period on the back upper left

corner of your blank paper.

One thing that is helpful for understanding when reading informational text is to make a picture of

what you read. Sometimes you do this in your mind, but putting it on paper and explaining to someone else helps you remember the meaning of the text.

Read pages 88, 89 & 116 in your textbook.

Draw a sketch that shows how energy and work are related. (You may use figure 1 on page 116 as an example, but

you must choose a different theme, activity, etc.)

After you draw, explain your sketch to your neighbor.

2. Write a caption for your picture on the front of the page; call your illustration Figure 1 and then explain what the picture

shows in 1 sentence.

3. On the picture, label any area where energy is displayed or

work is being done-(you MUST have at least 2 places

identified)

1. How are energy and work related?

2. Why is picking up a log work while carrying the log is not?

The amount of energy it takes to lift an apple 1 meter

The amount of heat energy released by a person at rest every 1/100 of a second

The KE of a tennis ball moving at 23 km/h(14mph)

How are energy and work being done during this

tennis match?

How are energy and

work being done

during a golf

tournament?

Energy of MOTION

Depends on speed and mass

KE = mv2

2

LOOK at the formula…

Which has a greater effect on KE,

mass or speed?

Why/how do you know?

Name: Period:___

ENERGY UNIT FORMULAS…

KE = mv2 2

Read pages 88, 89 & 116 in your textbook.

Draw a sketch that shows how energy and work are related. (You may use figure 1 on page 116 as an example, but

you must choose a different theme, activity, etc.)

After you draw, explain your sketch to your neighbor.

On the back of your paper, explain the following in a short

paragraph:

-Energy

-Work

-How your picture shows these 2 ideas

1. What are the 2 factors that determine the KE of an object?

Which has more KE-the red car or green car?

Explain.

Which has more KE-the red car or truck? Explain.

A snail with a mass of 5 g traveling at 0.014 m/s

has a KE of 0.00000048 J!

An 18-wheel truck traveling at 44 mi/h has a KE

of 2,200 J!

KE PROBLEMS…

1. What is the kinetic energy of a car that has a mass

of 1,200 kg and is moving at a speed of 20 m/s?

2. What is the kinetic energy of a car that has a mass of 2,400 kg and is moving at a speed of 20 m/s?

3. How does the kinetic energy of the 2 cars above compare? What do you notice?

Energy of POSITION or SHAPE Depends on weight and height The amount of work done to get object in

that position. GPE = weight x height

What’s the difference between

weight & mass?

GPE=weight x height

Does Diver A or B have

more GPE?

Which Diver did more

work?

Diver A

450 N

Diver B

500 N

Does Diver C or D have

more GPE?

Which Diver did more

work?

Diver D

550 N

Diver C

550 N

Which Diver did the most work?

Diver D

550 N

Diver C

550 N Diver A

450 N

Diver B

500 N

GPE PROBLEMS…

1. What is the gravitational potential energy of a book with a weight of 13 N at a height

of 1.5 m off the ground?

2. What is the gravitational potential energy of a cat that weighs 40 N standing on a table that is 0.8 m above the ground?

NOW…

1Read page 119 in your textbook.

2. Answer questions 1-3 on the bottom of page 119.

1. What is kinetic energy?

2. If the mass of a race car is 10kg and its speed is 20m/s, what is its KE?

NOW…

Let’s answer the questions 1-3 on the bottom of page 119.

NOW…

Watch the video about Kinetic and Potential Energy.

Answer the questions provided by your teacher.

NOW…

Read pages 120-123 Answer the 4 questions on page

123

KE FACTORS DEMO…

1. Copy the chart below into your notes.

# Washer

s Distance Traveled

Trial 1 Trial 2 Trial 3 Group Average

Class Average

1

3

5

2. Using the setup described on the paper at your table, launch the lid with the discs. Record your data.

3. Quickly graph your data.

4. Answer the 3 questions below:

1. What was the trend you observed as you increased the # of washers you launched?

2. Using the class average line on your graph, what would the distance have been for 2 washers?

3. What is the independent variable in this quick demo? Why/Explain.

1. What are the 2 factors that determine the KE of an object?

2. What is the formula for KE? 3. If the v of an object is 100

m/s and the m is 5 kg, what is the KE?

1. What is the difference between a dependent and an independent variable?

2. On which axis do we graph each?

3. Give an example of each from a recent science activity.

1. What are the 2 factors that determine the GPE of an object?

2. What is the formula for GPE?

3. How is weight different from mass?

The sum of the kinetic and potential energy.

ME = KE + PE

GPE=weight x height

ME= KE + PE

1. What is the difference between GPE and KE?

2. Why do we use mass for KE and weight for GPE?

Weight = 200 N

Mass = 20 kg

Heig

ht

= 5

m

What is GPE of the car?

What is KE of the car?

Weight = 200 N

Mass = 20 kg

Heig

ht

= 5

m

GPE = Wt * Ht = 200 * 5

GPE = 1,000 J

KE = m * v2 / 2 = 20 *02 / 2

KE = 0 J

Weight = 200 N

Mass = 20 kg

Heig

ht

= 5

m

What is the ME for this system?

Weight = 200 N

Mass = 20 kg

Heig

ht

= 5

m

ME = KE + PE

ME = 0J + 1,000J

ME = 1,000J

Weight = 200 N

Mass = 20 kg

Heig

ht

= 5

m

ME = KE + PE

ME = 0J + 1,000J

ME = 1,000J

GPE = 1,000J

KE = 0J

Weight = 200 N

Mass = 20 kg

Heig

ht

= 5

m

What is GPE of the car now?

What is KE of the car now?

Speed = 10 m/s

GPE = 0J

KE = 1,000J

Weight = 200 N

Mass = 20 kg

Heig

ht

= 5

m

Speed = 10 m/s

GPE = Wt * Ht = 200 * 0

GPE = 0 J

KE = m * v2 / 2 = 20 *102 / 2

KE = 1,000 J

What’s happening to the GPE as he rolls

down the hill?

Height decreases

so GPE decreases

What’s happening to the KE as he rolls

down the hill?

Speed increases

so KE increases

If the ME for this system is 1,000J,

what would expect the GPE and KE to

be at the half way point?

ME = 500J + 500J

More KE, less GPE

Almost all KE now

Weight = 200 N

Mass = 20 kg

Heig

ht

= 5

m

Speed = 10 m/s

ME = KE + PE

ME = 1,000J + 0J

ME = 1,000J

Wait a minute, Mrs. Lock! When

we tested this in the lab, the KE

at the bottom was LESS than the

GPE at the top. WHY???

Where did the energy go?

GPE = 0J

KE = 1,000J 850J

Some energy was changed into

heat and sound as the car

wheels rubbed against the ramp.

GPE = 0J

KE = 1,000J 850J

ME = KE + PE + friction!

1.Take out your textbook packet and clear your desks.

1.Take out your Finding Energy Lab papers

2.Finish this assignment and place it at the center of your table.

3.Work on the review sheet for the ME quiz.

1. Quickly finish your sheet from yesterday…then begin the review sheet.

1. What is ME? 2. When a car is at the top of a hill

and has not started moving, what type of energy will it primarily have?

3. When a car reaches the bottom of a hill and is going its fastest speed, what type of energy will it primarily have?

1. What is the

GPE for the

skier at

point A?

2. What is the

KE at point

A?

3. What is the

ME at point

A?

4. What is the

ME at point

B?

5. What is the

GPE at

point B?

6. What is the

KE at point

B?

Define:

◦Energy

◦Kinetic Energy

◦Potential Energy

◦Mechanical Energy

◦Work

1. What is the GPE at Point A?

2. What is the ME for the picture?

3. What is the GPE at Point B?

4. What is the approximate KE at Point B?

100 N

20 M

10 M

6. How does a

pendulum

show GPE

and KE?

1. How does a pendulum show KE and GPE?

Info: We want to see what affects the time a pendulum takes to swing. Time period is the time for a full swing (forward and backward). Question: How does length of the pendulum affect its time period?

Question: How does length of the pendulum affect its time period? Write your hypothesis using the question above. Remember it MUST be an “If…then…” statement. Use an independent and a dependent variable

Data:

Copy the chart below: Length of String (m)

Time for 20 Swings (s)

Time for 1 Swing (s)

1

2

3

4

5

6

7

8

9

10

Steps: 1. Measure the length of string 2. Measure the time for 20 full swings 3. Divide by 20 to find the time for 1 swing. 4. Repeat this for 9 additional string lengths 5. Graph the data (independent variable on the x-axis, dependent on the y-axis)

Steps: 1. Graph the data-time for 1 swing vs

length (independent variable on the x-axis, dependent on the y-axis)

2. Respond to the following on your graph paper in a good paragraph: Was the hypothesis correct or

incorrect? Why? Explain how energy is transferred in a pendulum. How does the Law of Conservation of Energy Apply to a pendulum?

Conclusion: Write a complete paragraph that explains the following:

What is energy? What are energy conversions? What is the Law of Conservation of Energy? What was the hypothesis Was the hypothesis correct? Why was the hypothesis correct or incorrect?

1. How does a pendulum show energy conversions?

2. What is the law of Conservation of Energy?

Steps: 1. Graph the data-time for 1 swing vs

length (independent variable on the x-axis, dependent on the y-axis)

2. Respond to the following on your graph paper in a good paragraph: Was the hypothesis correct or

incorrect? Why? Explain how energy is transferred in a pendulum. How does the Law of Conservation of Energy Apply to a pendulum?

Hot Shots 1. Describe the energy transfer between the hockey

player and the ice as he glides across it.

2. Why are hockey pucks stored in the freezer?

3. Why are composite sticks better than wood?

4. Why do hockey players slap their sticks on the ice before a slap shot? (use KE and PE in your answer.)

1. What is happening to energy at the top of a jump on a trampoline?

2. At the bottom?

1. On a ramp, where would you find the most potential energy?

2. Where would you find the most kinetic energy?

1. What kind of energy is found in a stretched rubber band? Explain.

2. What kind of energy in found in a rubber band that has been released? Explain.

1. Describe the energy conversions that happen as a skier goes down the slope.

2. Does ME change along the way? Explain.

Wt=50N

1.What is the KE at point A?

2.What is the PE at point A?

3.What is the ME at point A?

4.What is the PE at point B?

5.Use ME(and PE) to find the KE at point C.

Show work on back

Put answers on front

Rubber Band Racers…

We will build K’Nex Rubber Band Racers

We will use the windings of the rubber band as our unit of energy

We will “race” our cars and measure distance YOU MUST MEASURE DISTANCE IN METRIC

Determine your hypothesis AND procedure today

Figure out how you will accomplish all tasks tomorrow

1. Provide a caption for your work/energy picture

2. Label any area where work is being done (you should have at least 2

places where you have shown some work)

3. Put your name and class period on the back of your illustration

Decide whether each of the following is work or not…explain your answers. ◦ Pulling a wheeled suitcase

◦ Carrying a suitcase

◦ Picking up a bag of groceries

◦ Carrying a bag of groceries

On the back of your picture, please explain the following

in a paragraph:

-Energy

-Work

-How your picture demonstrates these 2 ideas

WARM UP…

Rubber Band Racers…

1. Build your car quickly; divide the jobs and work as

a team

2. Begin with 1 energy unit (1 winding) and run 3 trials for each number of windings; collect data

3. YOU MUST MEASURE DISTANCE IN METRIC

4. Take car apart; work on other items in lab if time remains

1. What is your hypothesis for the rubber band racers?

2. What is the independent variable?

3. The dependent?

Rubber Band Racers…

1. Average the data for each energy unit

2. Graph the average data for distance vs the energy units

Label the x axis including units

Label the y axis including units

Make sure your axes are evenly spaced

1-8 and 100-700

Put a title

3. YOU MUST USE DISTANCE IN METRIC

Rubber Band Racers Class Data…

Table 1

Table 2

Table 3

Table 4

Table 5

Table 6

Table 7

Table 8

Class AVG

1

2

3

4

5

6

Rubber Band Racers… Conclusion… IN A PARAGRAPH

Describe what energy is.

Explain the hypothesis.

Explain if the hypothesis was right or wrong and why.

Explain the relationship on the graph between energy and distance the cars traveled.

Explain why some other groups might have different distances.

KE PROBLEMS…

1. What is the kinetic energy of a car that has a mass

of 1,200 kg and is moving at a speed of 20 m/s?

2. What is the kinetic energy of a car that has a mass of 2,400 kg and is moving at a speed of 20 m/s?

3. How does the kinetic energy of the 2 cars above compare? What do you notice?

1.Which ramp would have a higher GPE?

2.What might be different about the different

ramps?