Program Information

Series: NASA Connect
Program: Rocket to the Stars
Segment Number: 1 (Watch entire program)
Duration: 00:13:42
Year Produced: 2004
Description:

First segment of Rocket to the Stars defines work and energy using the concepts of force, motion, distance, mass, height, and gravity. The work and energy segment covers the Gravitational Potential energy,and Kiinetic Energy equations. The Work and Energy segment next provides a problem that involves the calculation of the Kinetic Energy of 2 different rovers on the planet Mars.

NASA CONNECT™ is a series of Emmy®-award-winning, math-focused programs. Each program supports the national math, science, and technology standards and has three components that include (1) a 30-minute television broadcast; (2) a companion educator's guide; and (3) an online activity that further explores topics presented in the broadcast. These programs establish a connection between the math, science, and technology concepts taught in the classroom to those same concepts used everyday by NASA researchers.

For more information visit: http://connect.larc.nasa.gov/

Transcript

Hi, I'm Jennifer Pulley,
and welcome to NASA Connect,
the show that connects you
to math, science, technology,
and NASA.

Imagine it's the year 2040.

You and a team
of international scientists
are part of the exploration crew
that will begin construction
of the first human base on Mars.

You are laying the groundwork
for the next generation
of explorers
to explore Mars and beyond.

It's not an easy task,
but you are up to the challenge.

All your years of schooling,
training, and hard work
have finally paid off.

Does it sound
like a fantasy to you?

Actually, it's not.

NASA is ready
to make the next step
to exploring the solar system
and beyond.

And they need your help.

NASA is looking
for bright young engineers,
scientists, and researchers
who will make the new vision
for space exploration a reality.

For you, it starts right now,
in the classroom.

Now, during the course
of this program,
you will be asked to answer
several inquiry-based questions.

After the questions appear
on the screen,
your teacher
will pause the program
to allow you time to answer
and discuss the questions.

This is your time to explore
and become critical thinkers.

Students, working in groups,
take a few minutes to answer
the following the questions.

So, guys, how did you do
with the questions?

Great job.

Okay, let's get started.

So what is work?

Well, most people would say
they are working
when they do anything
that requires
a physical...
or a mental effort.

Now, in scientific terms,
work is the use of force
to move an object
a certain distance.

More specifically,
to do work on an object,
some part of the force you exert
must be in the same direction
as the object's motion.

Let's look
at the following two examples.

On the left side,
Norbert is lifting a stack
of textbooks from the floor.

And on the right side,
he is carrying
the stack of textbooks.

Note the direction
of the applied force and motion
for each example.

In which example
is Norbert actually doing work?

If you said the left side,
you are correct.

Why isn't Norbert doing work
in the example on the right?

Well, because no part
of the applied force
is in the same direction
as the object's motion.

When the force is in the same
direction as the motion,
we can determine the amount
of work being done on an object
by multiplying force
times distance.

What are the units for work?

You know that force
is measured in newtons
and distance can be measured
in meters.

The product of a force
measured in newtons
and the distance
measured in meters
is a measurement called
a newton-meter, or the joule.

The joule is the standard unit
used to measure work.

1 joule of work is done
when a force of 1 newton moves
an object 1 meter.

Do you have any idea
how much a joule of work is?

I know.

Let's take an apple,
which weighs about 1 newton.

Now, if you lift the apple
from the floor to your waist,
which is about 1 meter,
you do 1 joule of work
on the apple.

But what happens if I want
to lift 100 apples?

For me, that would take
a lot of force,
and I don't think I have
enough energy to do that.

Let's go back to our example
with the apple.

Now, I easily have enough energy
to lift this apple
from the floor to my waist,
and I know I'm doing work
on the apple as I lift it.

So there must be a relationship
between work and energy, right?

When I lifted the apple
from the floor,
I caused a change.

In this case, the change
is in the position of the apple.

An object that has energy
has the ability to cause change
or the ability to do work.

When I "worked" on the apple,
some of my energy
was transferred to the apple.

You can think of work, then,
as the transfer of energy.

As I lifted the apple
from the floor to my waist,
the apple gained energy.

You know, guys,
energy has many forms,
and we'll get to your list
in just a few minutes,
but first let's focus
on two forms of energy:
potential energy
and kinetic energy.

Let's take a look at each.

If I hold the apple still
in my hand,
does the apple have energy?

Careful; not all forms of energy
involve movement.

Well, this apple
has stored energy.

We call it potential energy.

Holding the apple like this
gives the apple the potential
to fall to the ground.

Now, if I release the apple,
the apple falls.

The potential energy changes
into kinetic energy.

It is pretty obvious when
an object has kinetic energy.

As long as the object is moving,
it's said
to have kinetic energy.

What's more difficult
to determine
is how much potential energy
an object has.

Let's go back
to our example with the apple.

The potential energy
of this apple
really depends on height,
how high or low
my hand is from the ground.

We call this type
of potential energy
gravitational potential energy.

Gravitational potential energy
depends on mass,
gravitational acceleration,
and height.

Near the Earth's surface,
gravitational potential energy,
or GPE,
is equal to the product
of mass, gravitational
acceleration, and height.

Remember that "g"
is the acceleration caused
by Earth's gravity,
which at sea level
equals 9.8 meters
per second squared.

Let me show you an example.

Suppose a satellite has a mass
of 293 kilograms
and we lift it to the top
of Mount Everest.

What is the gravitational
potential energy
of the satellite?

Well, what do we know?

We know mass is equal
to 293 kilograms,
gravitational acceleration
is equal
to 9.8 meters
per second squared,
and we know the height
of Mount Everest,
which is approximately
8,850 meters.

Let's write the equation for
gravitational potential energy.

Substituting in our values
for mass,
acceleration due to gravity,
and height, we get:

The answer turns out to be
approximately 25 million.

Don't forget I need to assign
a unit to that number.

Units are very important when
explaining scientific concepts.

Do you have any idea
what the unit for energy is?

Let's figure it out.

The original equation
for GPE is mgh.

Mass times gravity
is equal to weight,
and weight is measured
in newtons.

Remember, weight is a force.

Therefore, the unit for
gravitational potential energy
is the newton-meter.

Do you remember
from earlier in the program
what a newton-meter
is equivalent to?

Well, if you said 1 joule,
you're on the ball.

1 newton-meter is equivalent
to 1 joule.

Wait a minute;
work is also measured in joules.

I think
we just showed mathematically
how energy and work
are related to each other.

Now let's go back
to kinetic energy.

How much kinetic energy
do you think an object,
say like a rocket, depends on?

The kinetic energy
of an object depends
on both its mass
and its velocity.

The mathematical relationship
between kinetic energy, mass,
and velocity is:

Notice that the velocity
is squared in the equation.

Remember, guys, the number 2
is called an exponent.

The exponent tells you
how many times
a number or base
is used as a factor.

For example:

And so on.

So are you ready
to try a problem
involving kinetic energy?

Here's one for you.

Norbert's Mars rover,
with a mass of 210 kilograms,
is traveling
on the surface of Mars
at a speed
of 6 meters per second.

Zot's rover, with a mass
of 170 kilograms,
is traveling
on the surface of Mars
at 8 meters per second.

So did you make
the correct prediction?

Let's double-check your work.

Solving for the kinetic energy
of Norbert's rover, we have:

The kinetic energy
of Norbert's rover
is equal to 3,780 joules.

Solving for the kinetic energy
of Zot's rover, we have:

The kinetic energy
of Zot's rover
is equal to 5,440 joules.

So comparing the two values,
we see that the kinetic energy
for Zot's rover is greater
than the kinetic energy
for Norbert's rover.

We now know that an object
may possess both kinetic energy
and potential energy
at the same time.

Let's go back to our example
with the apple.

Any object
that rises and falls...
experiences a change
in its kinetic
and potential energy.

Let's look
at this energy transformation
as I toss the apple
into the air.

When the apple moves,
it possesses kinetic energy.

As it rises, it slows down.

Its kinetic energy decreases.

Because the height increases,
its potential energy increases.

At the highest point,
the apple actually stops moving.

At this point, it no longer
has kinetic energy,
but it has
maximum potential energy.

As the apple falls,
the kinetic energy increases,
and the potential energy
decreases.

No matter how energy
is transformed or transferred,
all of the energy
is still present somewhere
in one form or another.

This statement is known as the
law of conservation of energy.

As long as you account
for all the different forms
of energy involved
in any process,
you will find
that the total amount of energy
never changes.

In other words, energy cannot be
created or destroyed.

It just changes form.

So do you think you have
a pretty good idea
of what work and energy,
specifically potential
and kinetic energy,
are all about?

Well, good,
because now it's time
to preview this program's
hands-on activity.

Virginia Standards

6th Grade SOLs » Mathematics » 6.23
8th Grade SOLs » Science » PS.6
8th Grade SOLs » Science » PS.10