Or…Don’t let Gravity get you

down

Gravity. It’s the law. Obey it.

For the next clip, write down what you think is going through the person’s mind at the time. School appropriateness is crucial.

Also write down what you think might happen if gravity worked in a different way or if we were on a different planet.

In your notes…

BEFORE

What is going through his mind and what might this look like on a different planet or if gravity worked differently?

Remember… School appropriate

Songs by John Mayer, Sara Bareilles, Pixie Lott, Coldplay, A Perfect Circle

9.8 m/s2 Holds stuff downA force that attracts objects

togetherIncreases as the mass of the two

objects increasesDecreases as the distance

between the two objects increases

What is gravity?

Newton discovered gravity Its always the same If you drop two objects

from different places, they fall in parallel paths to the ground

The pull of planets and stars will affect the outcome of a persons life based on their position in the sky at the time of the individual’s birth

Misconceptions about gravity

When we drop things they fall down

The Earth orbits around the Sun

The Sun moves around the Milky Way

Objects follow a trajectory when launched at an angle

Your atoms stick together

Evidence for gravity

Newton’s Law of Universal Gravity

The nearer or more massive 2 objects are, the greater the force of gravity between them

F=G*((m1*m2)/d2) F is the force of attractionm1 and m2 are the masses of

the objectsd is the distance between

the objects G is the gravitational

constant

The Law of Gravity

Not discovered by Sir Isaac Newton

Found by measuring the force in Newtons between two masses of 1 kg each, 1 meter apart

0.00000000006667 N*m2/kg2

Or6.667 x 10 -11 N*m2/kg2This is a very weak forceThe crazy units make the end

result come out in NewtonsHow do you think this

machine works?

The Universal Gravitational

Constant

Cavendish Torsion Bar Gravity Balance

Scientific Notation

Scientific Notation

Used to make exceptionally large or exceptionally small numbers more manageable

Scientific Notation

If your starting number is large, you will have a positive exponent

If your starting number is small, you will have a negative exponent

Converting from regular to scientific

Move the decimal point so that it causes the number to be greater than 1 and less than 10.

Example:

5,200,000.

Converting from

regular to scientific

Next, count the number of times you moved the decimal point. This number will become an exponent.

5,200,000 = 5.2 x 106

Example:

0.0000314

3.14 x 10-5

Converting from scientific to

regular

The exponent indicates which direction the decimal moves

6.22 x 109

6,220,000,000

7.011 x 10-6

0.000007011

Linear speed - what we’ve already covered. Speed in a line

Rotational speed - Number of revolutions per minute

Tangential Speed – Speed of something moving along a circular path

Rotational Stuff

Centripetal Force – the force that causes an object to travel in a circular path

Centrifugal Force – a force that moves directly away from the center of a circular path

Rotational Stuff

Lets demo!!!Artificial Gravity – Can we make it?How?Are you really feeling gravity?What force are you feeling?

Rotational Stuff

When a quantity varies as the inverse square of its distance from its source.

Ex: the book uses an example of a “butter gun”

Inverse Square Law

Butter spray travels outward from the nozzle of the gun. Like gravity, the “strength of the spray obeys an inverse square law.

Questions1. What does the very small value of the gravitational constant, G, tell us about the

strength of gravitational forces?

2. What are the 2 masses and one distance that determine your weight?

3. Calculate the force of gravity on a 1-kg mass at Earth’s surface. The mass of Earth is 6x1024 kg, and its radius is 6.4x106 m.

Gravitational InteractionsGravitational Field- The type of force field that surrounds massive objects. (Such as planets, moons, and stars)

• Near the surface of the Earth, the gravitational field strength is 9.8 N/kg or 9.8 m/s2.

• At the surface of Earth, the gravitational force on an object it the object’s weight.

To find acceleration due to gravity on any planet, use the following equation:

g=GM/R2

Where G= gravitational constant, 6.67 x 10-11

M= mass of planet R= radius of planet

Gravitational Interactions

Question:

How does g at the surface of Jupiter compare with g at the surface of Earth?

Data: Jupiter’s mass is about 300 times that of Earth, and its radius is 10 times greater than the radius of Earth

Full weight=mg

Full weight=mg

Half weight= mg/2

Center= weightlessness=

Gravitational Field Inside a Planet• Gravitational fields exist inside

planets as well as around them.• Acceleration, g, would decrease as

you moved toward the center of Earth.

• At the center of Earth, your acceleration would be 0 m/s2. Why?

Ocean Tides

• Newton showed that tides are caused by differences in the gravitational pull of the moon on opposite sides of Earth.

• The moon’s attraction is stronger on Earth’s oceans closer to the moon, and weaker on oceans farther from the moon.

• How can you explain this?

Tides In the Atmosphere

The earth also has atmospheric tides that occur in the ionosphere.

These produce electric currents that alter the magnetic field that surrounds the Earth.

These “tides” regulate the degree to which cosmic rays penetrate into the lower atmosphere.

This can account for subtle changes in the behaviors of living things.

They are greater when the atmosphere is having its spring tides. Near the full and new moons.

The sun Two process

1) Gravity pulling the star in 2.) Fusion that blow solar material

outward.When they balance we get a sun.

If the rate increases the sun gets biggerIf the rate decreases the sun gets smaller

When it runs out of fuel it becomes a red giant and will be so big that it will swallow Earth.When the sun has burned all its fuel it will no longer give off heat and become a black dwarf.

Black Holes

For very massive stars (2-3x more massive than the sun) that burns out, gravity takes over and become infinite.

Collapse of space itself