MSP STEMDay 4

Discussion on Yesterday’s Probes

Work on Today’s Probes

Astronomy Probes

Here’s another approach for having your students present the solar system facts to each other.

Yes, you are going to present to us today

Solar System PBL / Math Pullout

Meteor’s & Meteorites

See separate Power Point

GravityIt’s a heavy topic!

Universal Gravitation

You are attractive to the person next to you!

Falling Bodies Newton knew that bodies continued in a

straight line unless another force acted on it (___ Law). What force kept the moon around the earth?

Moon must have _________ velocity to keep going, not away and not into, but around the Earth

This would have to be tested to be proven true to go from hypothesis to theory (law).

1st

tangential

Falling Bodies (cont.) Decided to use an apple to

compare movement of moon Known for Newton:

Moon 60 times farther than an apple Apple fell 4.9 m in first second Gravity is “diluted” by distance Moon should “fall” about 1.4 mm (and

it did as he proved by Geometry)

Falling Bodies (cont.) Newton put his findings away for

20 years until his “new branch” of mathematics (_______) helped further prove his calculations

This also proved the Copernican theory that the _____ revolves around the sun

Nothing crashes into the sun unless its tangential velocity is ______

Calculus

Earth

zero

Newton’s Law of Universal Gravitation Law states: “Every object attracts

every other object with a force that for any two objects is directly proportional to the mass of each object and inversely proportional to the square of the distance between them”

Or…F ~(m1)(m2)/d2

Newton’s Law of Universal Gravitation (cont.) Newton didn’t discover gravity,

just that it is universal. To put his law into a useable

equation, we have to establish the universal gravitational constant, G.

G = _________________This is very small because the force

is very weak

6.67 x 10-11 N•m2/kg2

Try One! Calculate the force of gravity

between a newborn baby (mass = 4.0 kg) and the planet Mars (mass = 6.4 x 1023 kg) when Mars is at its closest to Earth (distance = 8.0 x 1010 m).

2.67 x 10-8 N

May I have another? Calculate the force of gravity

between the same newborn and the obstetrician (mass = 75 kg), who is 0.30 m from the baby. Which exerted more force on the baby, Mars or the obstetrician?

2.22 x 10-7 N, Obstetrician

The Inverse-Square Law

The Inverse-Square Law (cont.) Similar to Mr. Hewitt’s butter gun,

the inverse square law is also applied to _________ and __________

If the distance between two objects doubles, the force between them is cut in ___________

In other words, the greater the distance from the Earth’s center, the less an object will weigh

gravity light

fourth

The Inverse-Square Law (cont.) See How to use the Rule of 1 on the

board... Two parts:

Replace whatever changed by the change factor

Replace everything else with a “1”. What happens to your weight if the

distance between the earth and you triples?

What happens to the force of gravity if both masses double?

Universal Gravitation Results Natural Proofs:

the Earth is round Planets deviate from their orbits when

they are near each other (perturbation)

Neptune and Pluto were found

Kepler’s Laws of Planetary Motion1. The paths of the planets are

ellipse with the center of the sun as one focus.

2. An imaginary line from the sun to a planet sweeps out equal areas in equal time intervals. Therefore, faster closer to sun, slower away from sun

3. (Ta/Tb)2=(ra/rb)3

Kepler’s Laws of Planetary Motion First two laws

deal with a planet or satellite individually.

Third law relates multiple planets or satellites to each other.

“r” in the third law is the average distance from the sun.

The “Rubber” sheet

Theoretical Gravity Activity

Calculating Your Weight

Books

Info on Fernbank◦ 10:00 AM◦ Meet in garden at front, Left◦ Missing Sign

Discussion on Today’s Probes

Wrapping up