Transcript Notes to Mrs. Kerns - Londonderry School District

The Physics of Astronomy:
How Motion Affects the Universe
Images from the
Hubble Telescope
Big Bang Theory

Previously we discussed one theory of how the
universe formed, the Big Bang Theory, where all
matter and energy was released approximately 14
billion years ago.
The Future of the Universe
Two factors
influence the future
of our universe.
 The first…
momentum of
matter in the
expanding universe

The Other Future Scenario
The 2nd factor for the future …
The inward force of gravity
These two factors are influencing
motion in the universe!
Why Study Motion in our Universe?

To know what kinds of observations to make.

To know how to accurately measure these
observations.

To know how to mathematically determine
measurements of motion.

To understand the relationships between objects
with motion and why it occurs rather than just
knowing that it occurs.
Scientists have been studying motion
for over 2300 years!
Artistotle, Aristarchus, Ptolemy, Copernicus,
Brahe, Galileo, Kepler, Newton & Hubble
Feel The Force

A force is a push or pull that can cause an object
to speed up, slow down, change shape or change
direction. You can’t see the force but you can
see what it does. Forces act on objects including
living organisms (that’s us!) all the time.
Friction is also a force that makes objects slow
down.
Why will objects in space be influenced by
forces?
Let the force work for you!

Imagine you are pedaling or
pushing your bike up a hill.
That push is a force. The result
of the force is that the bike
moves. If you pedal or push
harder with greater force the
bike will move faster. Then the
bike’s speed will increase. If you
were in a race each bike would
be traveling at different speeds!
The Speed is the rate (how fast) at
which an object moves. Does not keep
track of direction.
Speed = Distance
Time
Can be in miles or meters
Average Speed = Total Distance
Total Time
Example: 400 miles = 50 mph OR meters per second
8 hrs
What is the speed of the Earth
orbiting around the Sun?

Earth is also moving
around the Sun
counterclockwise at
about 67,000 miles
per hour!!!
What is the speed of our Solar
System moving within the
Milky Way Galaxy?
The solar system is about
26,000 light years from the
center of the Milky Way
Galaxy.
Our solar system travels
155 miles per second and
travels about 200-250
million years to orbit once
around the Milky Way.
How Fast Are Objects
Moving in the Universe?
Object
Average Speed
Earth’s Spin on Axis at the Equator
Earth’s Spin on Axis at Londonderry, NH
Earth’s Spin on Axis at North Pole
1, 038 mph
770 mph
1 cm/day
Earth’s Orbit Around Sun
18.5 mi/sec or 67,000 mph
Solar System’s Movement in Milky Way Galaxy
155 mi/sec
Milky Way Galaxy within Local Group (Cluster)
185 mi/sec
Which way did it go?

Scientists will use velocity to describe how fast
something is moving in a particular direction. It
is measured in meters per second or miles per
second.

If we are pedaling or pushing our bike from
LHS to the movie theatre at 20 miles per hour
the speed would be 20 mph and the velocity
would be 20 mph southeast.
Velocity

Velocity is the speed and direction of
an object’s motion. The rate at which
an object changes its position.

Direction can be: up/down, left/right,
to/from , East, West, North or South.

Example: 65 mph down
Measuring change

An object can change velocity by changing
direction even if it doesn’t change speed. An
object can also change its velocity by speeding up
or slowing down.

If our bike would speed up when we use more
force OR slow down when we get tired, OR if we
make a left hand turn with our bike we are
changing our velocity. Changing velocity is called
acceleration.
Acceleration is the rate at which
an object changes its velocity.
It is a rate of a rate!
You are accelerating if there is a …
1. change in speed
2. change in direction
3. change in BOTH speed and direction
Acceleration = Change in Velocity
Time
Units of measure: most likely meters/second2
or km/hr/sec or mi/hr/sec
Acceleration: Think it Over…
Acceleration has nothing to do with going
fast, you can be going very fast and not be
accelerating. WHY?
 If you slow down at a stop sign and start
again are you accelerating?
 If you rotate in a circle are you
accelerating?
 If you slow down at a corner & turn, are
you accelerating?

Acceleration Answers
Acceleration has nothing to do with going
fast, you can be going very fast and not be
accelerating? True
 If you slow down at a stop sign and start
again are you accelerating? YES
 If you rotate in a circle are you
accelerating? YES
 If you slow down at a corner & turn, are
you accelerating? YES

Two bike scenarios

Scenario 1:
You and your bike are
stopped waiting at a light
and a person (who looks
like the Hulk) hits you
with a strong force. You
and your bike fall down.
What is this
concept called?

Scenario 2:
You are riding your bike
and another bike hits you
with a strong force. You
and your bike fall down.
This concept is the same
concept from Scenario 1.
Newton’s First Law of Motion = Inertia
1. In regards to motion all matter has two
states
At Rest OR Moving
2. An object at rest tends to stay at rest and an
object in motion tends to stay in motion
with the same speed unless acted upon by
an unbalanced force.
3. Things keep doing what they are already
doing!
4. Inertia is the
resistance an
object has on it’s
state of motion.
5. Inertia is a
property of matter.
6. The greater your
mass then the
greater your
inertia.
Inertia
Inertia: Think it over…
If I slide a book across the table why
does it stop at the rest position?
 Is a force required to keep an object
going?
 An astronaut throws a rock in space far
from friction & Earth’s gravity. What
will happen?
 If you stop a car suddenly what
happens to a 80 lb child compared to a
200 lb man?

Inertia Answers

If I slide a book across the table why does it stop at the rest position?
Friction, The book would continue in motion with the same speed and
direction forever in the absence of friction or gravity.

Is force required to keep an object going? No

An astronaut throws a rock in space far from friction & Earth’s gravity.
What will happen? The rock would not stop but continue in motion in
the same direction.

If you stop a car suddenly what happens to a 80 lb child passenger
compared to a 200 lb man passenger? The seat belt would be the
external force that would stop them as the body wants to go forward.
The more mass you have the harder the force would be to stop the
object or person.
Food Fight
Jim and Bob are arguing in the cafeteria.
Jim says that if he flings Jell-O with a
greater speed it will have a greater inertia.
Bob argues that inertia does not depend on
speed.

Who do you agree with?

WHY???
Food Fight Answer
Bob is correct because inertia depends
upon mass.
 The more mass the more inertia.

Roller Coasters!

You probably know that
when you ride a roller
coaster you need to be
strapped in.

WHY?
(using science terms)
Roller Coaster Answer
Your body will want to
continue moving in the
direction it is traveling!


That is why there are weight limits on rides
because the strap can’t hold larger
masses.
Baseball Pop Up Throw
 The ball wants
to continue in
motion due to…
 Describe what
is happening in
the picture.
 Use 3 science
terms
Baseball Answer



The ball wants to
continue in motion
(inertia) but forces are
acting upon it to
change its direction.
Gravity
Air resistance or
friction
What Matters?
You are back on your bike but this time you
are carrying an elephant in your bike’s basket
and your friend is carrying a puppy in their
basket. You both are traveling at the same
velocity but a car zooms out in front.
 Who will have a more difficult time stopping
their bike?
 WHY???

Mass Matters!

The elephant has more mass! Therefore
you will have a more difficult time
stopping.
What else matters?

This time you and your friend both have a
twin puppies in your bike’s basket. Although
you are pedaling with more force therefore
with more velocity than your friend. A car
again zooms out in front of you both.
Who will have a more difficult time
stopping their bike?
 WHY???

Velocity Matters!

You are traveling at a greater velocity than
your friend. Therefore it will be more
difficult for you to stop!

Why?
Momentum = Inertia in motion
1. Inertia depends on mass
2. Momentum depends on mass and
velocity (speed with direction).
3. A mass can have momentum only
when its moving.
Momentum = mass
P = mv
X velocity or
Momentum’s relationship with
mass & velocity
1.
2.
3.
4.
Momentum is directly proportional to
mass or is dependent upon mass.
If mass increases then momentum
increases.
Momentum is also dependent on velocity.
If velocity or speed increases then
momentum increases.
Momentum

When an object has more mass OR when
an object is moving at a higher velocity it will
have more momentum.

Momentum is how forcefully an object is
moving in a particular direction. If an object
such as an elephant has a lot of mass it is
hard to start moving the elephant. But once
the elephant is moving it is harder
to make the elephant to slow down
or stop.
Momentum: Think it over…

1. If velocity decreases what happens to
momentum?
Momentum: Think it Over…
2. If you were going to be hit by a vehicle
both traveling at the same speed which
one would you prefer…
 a Smart Car or a Hummer?
 WHY?
Think it over
Momentum answers


If velocity decreases what
happens to momentum?
decreases
If you were going to be hit by a
vehicle both traveling at the
same speed which one would
you prefer…
a Smart Car or a Hummer?
Why? A Smart Car because
the vehicle with less mass has
less momentum.
Hubble’s Law


According to Edwin
Hubble, the Universe
is currently expanding
and still expanding.
In 1929, Hubble
discovered (using
spectroscopy) that
galaxies are moving
away from us in
proportion to their
distances from us.
Visible Light



Visible light is the light
you can see and the
colors are represented as
ROYGBV
When all the wavelengths
are viewed together they
make white light.
Spectroscopy uses only
visible light from objects
in space.
Spectroscopy



Each color has a
different wavelength
Violet has the
shortest wavelength
and highest energy
Red has the longest
wavelength and
lowest energy
Hubble’s Red Shift Discovery




Hubble examined the
light from stars in the
distant galaxies.
He found that the pattern
of spectral lines of the
elements was shifted
toward the red end of the
spectrum.
Red Shift = Objects that
are moving away
Blue Shift = Objects that
are moving toward us
Hubble’s Conclusion

Hubble concluded that if stars in distant galaxies
were moving away from us (as evidenced by the
red shift of their spectral lines), then the universe
is expanding.
Doppler Effect:
Sound and Light
Waves
When an object is moving
away from us, any energy
waves emitted will be
stretched out to form
longer, lower energy
waves. Any object moving
towards us would produce
the opposite effect —
shorter, higher energy
waves. Thus, a siren is
louder when it is moving
toward you and is emitting
short, high energy waves.
Bibliography
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What’s Physics All About by Kate Davies
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