potential and science kinetic energy › d4114312 › files › ... · 2019-10-20 · potential •...

potential • kinetic • friction • momentum • velocity • acceleration • gravity • inertia

SciGen Unit 8.1

POTENTIAL AND KINETIC ENERGY

SCIENCE ACTIVITIES

Session 1 Reader’s Theater

2–5

Session 2 Speaking Scientifically

6–11

Session 3 In the Lab

12–13

Session 4 Getting a Grip on Gravity

14–16

Session 5 Writing

17–19

SUPPLEMENTARY ACTIVITIES FOR OTHER CONTENT AREAS

ELA The Gravity of Gravity

20

Math Speed vs. Velocity

21

Social Studies History of the Roller Coaster

22

FOCUS WORDS

Examining the Focus Words Closely 23

science

© 2015 SERP SciGen Unit 8.1 1


Cooper: You look half dead, Hamza. Here, take my energy bar.

Hamza: Thanks. I get that the bar will give me some energy, but I did not get last night’s homework about energy. Did you?

Olivia: Hi guys! I thought the homework was confusing, too. It said something about energy having to do with things moving, but energy bars don’t move. At least not like a ball or a wave does.

Cooper: Maybe they’re called energy bars because they can make people move more when they eat them? I don’t know, though.

Hamza: I thought energy was electricity that makes stuff work, like lights.

Olivia: Maybe energy can do a lot of different things. But then why bother with the word “energy”? Why don’t we just say “food” when we mean food and “electricity” when we mean electricity?

Hamza: I think that this energy bar is working. I feel better. My energy had gone on vacation, and now it’s...coming home.

Cooper: You know, your energy might have come back, but the energy we are studying never goes away, it just changes. Look...

He pulls out his homework and points to this graphic:

Cooper: Remember how the energy of the sliding book was slowed down by friction so the table and the book got hotter? Well, probably just a little hotter. Anyway, that’s where the energy went, into heat.

Olivia: Are you saying that hotter people use more energy? Well, that means that Hamza...

Hamza: (cutting her off) Don’t go there, Olivia.

Cooper: (changing the subject) Look at the next picture. We’re supposed to explain what’s going on in terms of energy.

Olivia: Whoa, there’s a lot going on there. It’s confusing. It’s like everything is all connected. How can you even keep track of what you’re talking about?

Hamza: The fan is winding up the thing attached to the stand. When you turn the fan off the mass is going to drop back down because of gravity. What a crazy setup.

Olivia: You totally could have done your homework if you’d tried. You got that way faster than I did. So this weird energy system is storing up energy as the string gets wound up.

Cooper: Yeah. The kinetic energy involved in the winding up is getting switched over to potential energy.

Hamza and Olivia: Huh?

Ms. Quintanilla: Sorry, guys. I couldn’t help eavesdropping because I was so impressed with your comments. Especially yours, Olivia, about the challenge of keeping track of different parts of a system.

Olivia: I said that? Uh, I mean thanks, Ms. Q!

Ms. Quintanilla: System is a great word in science because it’s flexible. It’s like drawing an imaginary boundary around a portion of the real world and studying how the parts within it work together. Let’s look at the last part of your homework with that hillside problem.


Speaking ScientificallyReader's Theater

Session 1

Keeping Track of EnergySetting: Cooper, Olivia, and Hamza had a hard time with their science homework last night. They’re talking in the hallway before class.


Hamza: That was hard!

Ms. Quintanilla: It’s supposed to be hard. When things are easy you’re not really learning, you’re just performing. Remember that these exercises were supposed to help you begin thinking about energy. If you’re struggling, that means you’re thinking! We’ll discuss them right now in class.

Hamza: Oh good. I’m glad. I didn’t understand what you meant by potential and kinetic, either.

Ms. Quintanilla: Excellent question. We’ll go over that as well.

They all walk into the classroom. Ms. Q asks the class to look at five images of the hillside (part of their homework). She tells the members of each table group to compare answers and to discuss their thinking. Cooper, Hamza, and Olivia are sitting at the same table, and they all have different answers to the problem. Here’s how the problem looked on their worksheet:

Ms. Quintanilla: In fact, we can use these little pictures to help us with a few more helpful terms we need to learn: momentum, acceleration, velocity, and inertia.

Olivia: I hear the first two of those words all the time. Our lacrosse coach talks about momentum a lot.

Hamza: And you hear about acceleration in car commercials.

Ms. Quintanilla: Great! Well, let’s talk about the science so you can see why coaches and advertisers like the terms so much.

The five illustrations show an energy system but they aren’t in the correct order. Think through how the energy would move through this system. Then cut out the the images and tape them on another piece of paper in the correct order.


Reader's Theater

Session 1

Keeping Track of Energy


Ms. Q draws on the whiteboard:

Cooper: (under his breath) I’m glad she’s our science teacher and not our art teacher...

Ms. Quintanilla: (to the entire class) My extra credit starter challenge for you all today is to look at the last problem of your homework, the one with the hillside, and to add a caption that describes what’s happening in the sequence. But try to use the terms I’ve written on the whiteboard correctly as you write.

Hamza: Extra credit? Awesome. This will help make up for the other times when I didn’t have the energy to do my homework.

Olivia: I say again Hamza, not an energy problem...an attitude problem.

Hamza: Whatever.

Something that’s moving has momentum.

Velocity is how quickly something is moving in a particular direction.

Acceleration describes how the velocity is changing.

Inertia is the tendency for objects at rest to remain at rest (OR to keep traveling at the same velocity if they are traveling).


Reader's Theater

Session 1

Keeping Track of Energy


Here is Hamza’s sequence:

Here is Hamza’s caption: The ball on top of the hill is still because of inertia. The ball’s velocity increases as it goes down the hill. The block stops the momentum of the ball so it’s not accelerating.

Would you change Hamza’s sequence? yes | no How would you improve Hamza’s caption? _________________________________________________________

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Here is Cooper’s sequence:

Here is Cooper’s caption: The ball had lots of momentum, so there’s a big BUMP because inertia would cause the block to want to stay still and the ball to keep rolling. The second time the ball hit the block there’s less velocity because it did not roll down the whole hill.

Would you change Cooper’s sequence? yes | no

How would you improve Cooper’s caption?_________________________________________________________

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Here is Olivia’s sequence:

Here is Olivia’s caption: The velocity increases and that is acceleration. The block doesn’t move very much when it is hit because of inertia and friction.

Would you change Olivia’s sequence? yes | no

How would you improve Olivia’s caption? __________________________________________________________

__________________________________________________________________________________________

Below are clippings from Hamza’s, Cooper’s, and Olivia’s homework assignments. Evaluate their sequences and captions and then answer the questions about their work.


Reader's Theater

Session 1

Comprehension Questions


Energy surrounds us and is part of everything we do. It’s so common that it can be difficult to talk about. One way to help us understand energy is to sort things with energy into two big categories.

I. Kinetic Energy: the energy of motion.

This ball has kinetic energy because it is moving.

The word “kinetic” in English comes from the Greek word kinetikos (moving).

Look around you right now. List three things with kinetic energy and compare your answers with someone else in the class.

__________________________________________

__________________________________________

__________________________________________

What did you see? A tree branch swaying outside the window? The second hand on the clock? Or perhaps the heads of other students turning about looking for examples of kinetic energy?

II. Potential Energy: the energy of relative position or shape.

This ball has potential energy. It’s not moving right now, but it could if the girl let go of it. The ball’s position relative to the Earth has given it potential energy.

Potential energy is all around you too, but it might be a bit harder to spot. Do you see anything with potential energy around you? Anything that is inflated? Propped up? Hanging? Usually these are examples of things that are not moving but could if something happened. They have the potential to move.

List three things with potential energy.

______________________________________

______________________________________

______________________________________


Speaking Scientifically

Session 2

Kinetic vs. Potential Energy


1

23

Sometimes objects have both kinetic and potential energy. Let’s say that Child #1 is just sitting on the swing and not moving at all. Child #2 is moving backward. Her position moments ago was just like Child #3. Speaking of Child #3, he is at the very highest point of his swing.

TURN AND TALK

Of the three children swinging, which is displaying the most kinetic energy? The most potential energy?



Session 2

Kinetic Energy (KE) and Potential Energy (PE) Within a System


To make a pendulum:

Tie a metal washer to the end of a 50-cm piece of string.

Hold the pendulum at the non-washer end.

Ask another student in your class to give the pendulum potential energy by moving the washer about 30 cm to the right or left.

Have your helper let go of the washer so it can swing.

TURN AND TALK

Energy transformations are taking place here.

1. Where?

2. When?

3. What happens if you just let the pendulum swing for awhile?

4. What happened to the energy?

A pendulum might help you better understand how kinetic and potential energy are both present in the swing set on the previous page.



Session 2

Transfer of Kinetic Energy (KE) and Potential Energy (PE) Within a System


When your partner moved the washer to the left or right from its resting position, he or she gave the pendulum potential energy. It was potential energy because the washer could swing due to its relative position and gravity. This kind of potential energy is known as gravitational potential energy.

What’s interesting about a pendulum, though, is that when you let go of it, the potential energy gradually transforms into kinetic energy. And then it gets faster and faster until it reaches the lowest point of the swing. At that point the kinetic energy starts transforming back into potential energy on the other end of the swing. Then, the pendulum actually comes to a stop! It comes to a stop for a very short time at the end of each swing. When it is “at rest” the energy is once again potential energy.

With this great system going, you might think the pendulum would never stop. But as you observed, it does indeed stop swinging after a while. But why? Where did all that energy go?

TURN AND TALK

What on Earth is this weird-looking graph trying to tell us?



Session 2

About the Pendulum and Its Energy


The washer (and the string) is actually banging into something as it swings. But what? AIR MOLECULES, of course! Swing your hand back and forth and feel them for yourself! But an even more significant reason for the pendulum slowing down is the friction between the string and your fingers and the friction of the different parts of the string itself.

TURN AND TALK

What on Earth is this even weirder-looking graph trying to tell us?



Session 2

Friction


Check the appropriate box next to each image. KE stands for kinetic energy. PE stands for potential energy. Don’t hesitate to check the “unsure” box. Not knowing the answer right away is a GOOD thing in science class!

PE

KE

both

unsure

PE

KE

both

unsure

PE

KE

both

unsure

PE

KE

both

unsure

PE

KE

both

unsure

PE

KE

both

unsure

TURN AND TALK

Compare your responses with someone else in your class. Discuss.



Session 2

Try It Out!


Rubber Band Lab: Can you use measurements to study the relationship between potential and kinetic energy within a system?

You will need:

• a rubber band

• a Styrofoam or paper cup sliced in half lengthwise

• a ruler

Procedure:

1. You will stretch your rubber band 3 different lengths – short stretch, medium stretch, and long stretch. Each length of the rubber band is a “condition” of your experiment.

2. Conduct 3 trials for each condition.

3. For the 3 trials for each condition, make sure the rubber band is stretched exactly the same length and that the cup starts in the exact same place.

4. Carefully aim the rubber band at the same spot on the cup (so the cup will move in the same direction).

5. Record how far the cup moves for each trial. Then calculate the mean distance for each of the 3 conditions.

Potential energy (represented by rubber band stretch):

Length of rubber band stretch = ______ cm

First Trial: Cup moved ______ cm

Second Trial: Cup moved ______ cm

Third Trial: Cup moved ______ cm

Kinetic energy (represented by cup movement):

mean cup movement = ______ cm

Condition 1

(short stretch)








Condition 2

(medium stretch)








Condition 3

(long stretch)

How to cut a cup in half lengthwise...


In the Lab

Session 3


TURN AND TALK

Do you see a trend? Do these data support any ideas you might have about the relationship of potential and kinetic energy in this system?

Rubber band stretch

Cup

mov

emen

t

Analyzing your data from the Rubber Band Lab

Restate your results here. Then graph them below.

Condition 1: When the rubber band was stretched ________ cm, the cup moved an average of ________ cm.




In the Lab

Session 3


All through history people have asked the same questions, like “What's for dinner?” and “Why do things fall?” Aristotle, who lived in Athens almost 2,500 years ago, argued that the center of the Earth was the center of the universe. So naturally everything tended to fall in that direction! Wrong on TWO counts. He also thought that heavier things fell faster than lighter things. Well, you could see how he would think that. Try dropping a piece of paper and a book. The book hit the floor first, right? But not because of gravity and not because it is heavier.

WHAT? Here is where Galileo comes in. He carefully dropped balls from towers and rolled them down inclines. He stated that the reason your book drops faster than your paper is not due to their difference in mass, but rather because air resistance (friction) affects the falls differently.

Explore Galileo’s idea.

Step 1: Go to the moon.

Step 2: Drop a feather and a hammer at the same time.

Oh, going to moon is not in your budget? Well, watch this video of two astronauts who tried it out:

As great as Galileo was, Isaac Newton was the one who really hit it out of the park with this idea: He said that gravity is not just about the Earth pulling things, but rather that everything that has mass creates a gravitational force.

Gravity n. A force that acts between all masses, pulling them together. Is the definition helpful?

Sort of. Not really. Seriously?

(Thanks for the video, NASA!)


Getting a Grip on Gravity

Session 4

http://wordgen.serpmedia.org/apollo.html




Consider an apple and the planet Earth.

Newton said that the apple is pulling on the Earth in exactly the same way as the Earth is pulling on the apple.

Huh? Then, you might ask, “Why doesn’t the Earth fall up to the apple?” Well, the answer to that is...

It does.

Huh?? Just not very much. Actually, it’s an immeasurably small distance.

So, how can the apple and the Earth react to equal forces so differently?

To understand this, think about applying an equal force to two things with very different masses.

Why wouldn’t the car move as much as the paper clip??

INERTIA.

Massive things have more mass (duh!), more gravitational force, and more inertia. If you think that car was hard to move with a flick of your fingers, just imagine how tough it would be for the apple’s gravitational field to yank the Earth up to it. Not gonna happen!

LAST question: The acceleration of the apple dropping to the Earth is

◻ greater than

◻ less than

◻ about the same as

the acceleration of the Earth up to the apple.

1. Think about flicking a paper clip with your fingers.

2. Think about flicking a parked car with your fingers.

!!



Session 4

Greater than, of course! You can definitely observe that.

But why?


Gravity causes the apple to move toward the Earth and yes, the Earth to move toward the apple (good luck observing the latter). You can measure movement (of the apple at least) using velocity. If the velocity changed along the way, you can describe that as acceleration. The apple’s fall to Earth started slow and got faster. There is all kinds of interesting math about the details of that. Ask your science teacher to explain more if you’re interested. But don’t get carried away. You have to save something for high school!!

The important thing here is to remember that when we think about gravity, it’s easy to think about it as the Earth pulling on things. And that’s true. The Earth does, indeed, pull on things. But keep in mind that everything else that has mass pulls on things, too. The Earth tends to get our attention the most because it’s the biggest thing around pretty much everywhere we hang out!

If you compare the Earth to the Sun, the Earth is a little more like the apple in that situation. The Earth is affected by the Sun’s gravity in a major way, but also by all sorts of other interesting forces in the universe. (Good thing, too...or we’d be toast! Burnt toast at that!)



Session 4


54 m 35 m

A drawing is a great way to make a model, but here is another idea to really help your little cousin understand.

The second coaster might seem safer, but...

You’re taking your little cousin to the amusement park for the day and it’s your job to keep him safe. You really want to go on the roller coaster, and he says he really wants to as well. But you predict that when he sees how tall the roller coaster is at the park, he may back out. He’s always afraid of getting hurt. Thinking ahead, you draw the pictures below for him to make a point that sometimes taller and faster is better.

Think about what you now know about potential energy. Is there more potential energy in the car poised at the top of roller coaster A or in the car at the top of roller coaster B? If you answered A, you’re right! And roller coaster A uses more kinetic energy and momentum to get through the entire ride safely. Though roller coaster B LOOKS less scary, the truth is that it might not have enough energy to get through the loop. Riders might not make it all the way to the end of the ride!

Supplies used to make this model:

Plastic tubing from the hardware store

Marble

Ruler

� � , � � � � � �� . � � �,� , � � � � � � � � � �

, ,� � , �

Roller Coaster A

Roller Coaster B

54 m 35 m 39 m 35 m

35 cm


Writing

Session 5

Scripting a Demonstration for Younger Students


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It’s your turn to share your knowledge about roller coasters and energy with a classroom of second graders. Your goal is to make sure the students understand that roller coaster A is safer than roller coaster B and why. How will you explain this in a clear, simple way? You might want to create a simulation, like the one on the previous page, to make it easier for the kids to grasp the concepts. Or feel free to come up with another fun and effective way to convey your information. Write a script as if you are speaking directly to the students. Don’t forget to introduce yourself!

Explanation for younger students:


Writing

Session 5

Scripting a Demonstration for Younger StudentsRoller Coaster A

Roller Coaster B


Now provide the same explanation as on the previous page, but for a different audience. For example, write as if this roller coaster question is on the application to the high school you would like to attend.


Writing Prompt

Session 5

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Explanation for high school application:

Roller Coaster A

Roller Coaster B

Writing for a Different Audience


Consider an experience you’ve had that was emotionally or physically intense. Maybe someone you really thought you could depend on disappointed you? Or you found yourself in a situation that pushed your body to the limit? Now see if you can write about it, either in poetry or prose, using one or more of the focus words below.

‣ gravity

‣ kinetic

‣ friction

‣ momentum

‣ velocity

‣ acceleration

‣ inertia

‣ potential

If you’d like, see if these additional words inspire you. Scientifically speaking, they describe forces and the different ways that forces can make an object change shape. But they have other meanings, too, which you’ll probably recognize.

‣ distortion

‣ tension

‣ stress

‣ compression

‣ strain

Having trouble? Need a jumpstart? Try writing an acrostic poem. Choose a word and then write it down vertically. Let each letter be the beginning of a word. Feel free to add more words per letter or get creative in other ways.

Finally,

Rain comes.

I’m

Crying

Twice as much as the heaviest downpour.

I can’t believe you

Only closed the door.

No goodbye.


The Gravity of Gravity

ELA

The language of science is powerful. Words used to describe the forces that help us make sense of our universe have a unique place in the world of words. When used in poetry or creative writing, they’re able to move us, challenge us, and change us because they connect us to something much bigger than ourselves.

Think of the word “gravity.” The nonscientific meaning of the word is “seriousness” or “importance.” But how heavy the word feels! We can’t help but imagine, either consciously or unconsciously, the pull of planets, that tremendous force that influences how Earth orbits the Sun.

An acrostic poem using the word “friction”:


Speed is a type of rate that measures how long it takes to travel a distance.

Velocity measures how fast something is moving plus the direction that the object is moving. So a car driving from Baltimore, Maryland, to Norfolk, Virginia, might have a velocity of 70 miles per hour south.

Consider this:

On Monday, you rode your bike on the direct road from point A to point B in exactly one hour without stopping.

On Tuesday, you rode your bike on the curvy road from point A to point B in exactly one hour without stopping.

Did you ride your bike at a greater average speed on one of the roads? Absolutely!! The curvy one!

Point A

Here’s another problem to think about:

On Wednesday, you rode your bike at 15 miles per hour from Point A to Point Y. On Thursday you rode your bike at 15 miles per hour from Point A to Point Z. That means that you traveled at the same speed on both Wednesday and Thursday. Right? Right.

But in this case, the average velocity is not the same.

TURN AND TALK: Why is the average velocity different?

Point A

Point B

Monday route

Tuesday route

Point Y

Point Z


Speed vs. Velocity

Math

Are we splitting hairs, or is there really a difference?

TURN AND TALK: How do you know?

Here’s the weird part: Your overall (or average) velocity on Monday and Tuesday is the same. But how can that be? It’s because you measure average velocity using only the start and end points and by referring to direction. So if Point B is 15 miles east of point Point A, that means that your average velocity was 15 miles per hour east.


The modern roller coaster descended from towering ice slides in Russia, which first appeared in the 17th century. Referred to as “Russian Mountains,” these slides provided entertainment throughout Russia, though they were most prevalent in the area that would later be known as St. Petersburg. Rising up between 70 and 80 feet in the air, the slides were made from lumber that was covered with several inches of ice and offered riders an exhilarating 50 degree drop. The slides were reinforced with wooden supports and had steps up the back for riders to climb before speeding down on sleds. Popular with the upper class, some slides were ornately decorated. An enthusiastic fan of the slides, Catherine the Great reportedly had several built on her property.

Historians debate who deserves credit for adding wheels and creating the roller coaster as we know it. Some contend that the Russians invented the first roller coaster, which was constructed in the Gardens of Oreinbaum in St. Petersburg in 1784. Other historians argue that the French are responsible for the first roller coaster. Les Montagnes Russes à Belleville (The Russian Mountains of Belleville) was built in Paris and had many of the features we associate with the modern roller coaster, including guide rails, cars with wheels that lock to the track, and plenty of speed. It is also likely that Paris was home to the first permanent loop track, built in 1846 from an English design, and referred to as a “centrifugal railway.” It was constructed with a wheeled sled, which held one person and traveled through a 13-foot-high vertical loop.

In the 1820s, the United States made an impact on the development of the roller coaster. A mining company in Summit Hill, Pennsylvania, created an 8.7-mile downhill track in order to deliver coal to the town of Mauch Chunk. When the mine closed in the early 1870s, the track was dubbed "Gravity Road" and continued offering rides to thrill-seeking visitors for a price. A Sunday school teacher from Ohio, LaMarcus Adna Thompson, believed in the potential for wholesome fun that this type of entertainment could provide young people. He began to work on his own gravity switchback railway. In 1884, Thompson’s Gravity Pleasure Switchback Railway opened in Coney Island, and America’s first true roller coaster was born!

Activity

You and your partner are going to simulate an interview. Pretend the interviewer is a historian from a distant galaxy who is working on a report about Earth, but he or she is completely confused as to why Earthlings would invest in roller coasters. The role of the person being interviewed is an eighth-grade student who loves roller coasters and knows about potential and kinetic energy. He or she attempts to explain why they are fun. The interviewer seems to understand the science, but not the fun part. The eighth grader tries to connect the two.

LaMarcus Thompson’s Switchback Railway (1884)


History of the Roller Coaster

Social Studies



Examining the Focus Words Closely

Focus Words

SciGen Unit 8.1

Scientific or Everyday Use Definition Try using the word...

potential energy noun

the energy an object has because of its relative position

What objects around you have potential energy?

potentialnoun

possibility, such as talent or skill that may be developed later

Do you have the potential to become an athlete? A musician? A scientist?

kinetic energy noun

the energy of motion The kinetic energy of falling water can grind wheat into flour, saving human effort. Can you think of something else powered by kinetic energy?

kineticadjective

relating to motion Kinetic works of art, such as mobiles, are very popular. Can you think of other examples?

friction noun

the force slowing the motion of objects due to interactions along their surfaces

Do you think there is more friction with a steel wheel on a train track or with a rubber tire on asphalt?

frictionnoun

a conflict between people or personalities

Describe a situation that might cause friction between two students.

momentum noun

the quantity of motion of a moving body (mass x velocity)

How does a roller coaster’s momentum enable it to climb hills and complete loops?

momentumnoun

a driving force in a process If you fell behind in a competition, how would you motivate yourself to gain enough momentum for a comeback?

velocity noun

the speed in a certain direction

Explain a situation in which velocity changes even though speed stays constant.

acceleration noun

the rate of change of velocity per unit of time

A roller coaster train accelerates as it descends. Why?

accelerateverb

to gain speed; to make something happen faster

Name some technologies that help accelerate processes in your daily life.

gravity noun

a force that acts between all masses, pulling them together

Everything that has mass has a gravitational field. Why is Earth’s gravity the most obvious to us?

gravitynoun

extreme or alarming importance; seriousness

When might the gravity of a situation cause a bystander to intervene?

inertia noun

the property of matter by which things continue their current motion (either going straight at the same speed or staying still), unless a force acts upon them

More massive things tend to have more inertia. Can you think of an example?

inertianoun

the tendency to remain inactive or unchanged

Sometimes people blame inertia for the public’s reluctance to invest in cleaner technology. Do you think this is a fair assessment? Explain.

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