g ravity and m otion *** what keeps the earth and the moon in orbit? *** *** why don’t they just...
TRANSCRIPT
GRAVITY AND MOTION
*** What keeps the Earth and the Moon in Orbit? ***
*** Why don’t they just fly off into space? ***
SIR ISAAC NEWTON First person to answer questions about
gravity and motion. Discovered his theories in 1666 He realized there must be a force acting
between the Earth and the moon and the Earth and the Sun.
GRAVITY Gravity attracts all
objects toward each other
He didn’t invent or come up with gravity but he was the first person to realize it happens everywhere.
Law of Universal Gravity every object in the universe attracts every other object
The strength of gravity between two objects depends on:
The mass of the objects
Distance between them
PEN
NY
EX
PER
IMEN
T
DISCOVER ZONE-GRAVITY Get into lab partner groups and then listen
for directions You will need: A ruler, stack of pennies, a
sheet of paper Procedure
Place the stack of pennies on the table Write down a prediction if you were to swipe the
bottom penny out Quickly slide a ruler along the surface of the
table. Observe what happens to the stack Repeat several times, knocking more pennies
from the bottom of the stack.
Why don’t we notice a pull between you and the book? Or you and the ball? Or you and the ground?
The strength of gravity depends in part on the masses of each of the objects.
GRAVITY
Mass is the amount of matter in an object The more mass an
object has the more gravitational pull
Weight is the force of gravity on an object This can change
depending on place
Distance between two objects. When the objects
are close together the gravitational pull is stronger
When the objects are farther apart the gravitational pull is less
Mass and Weight Distance
Regular
Large
small
MOVIE CLIP
Look into the basics of gravity with a movie clip from discovery education:
http://player.discoveryeducation.com/index.cfm?guidAssetId=B8FD0AAA-0355-4617-ACD9-B7C08EC61262&blnFromSearch=1&productcode=US
INERTIA AND ORBITAL MOTION
Inertia The tendency of an object to resist a change in motion. In the car, a seat belt An object with greater inertia is harder to stop
Newton’s first law of motion an object at rest will stay at rest and an object in motion will stay in motion with a constant speed and direction unless acted on by a force. Demonstration with a marble
WHY DO THE EARTH AND THE MOON REMAIN IN THEIR ORBITS WITHOUT RUNNING INTO EACH OTHER?
View diagram to see how gravity and inertia are combine to keep the moon orbiting around the Earth.
ASSESSMENTS
THINK , PAIR , SHARE
1. WHAT IS THE LAW OF UNIVERSAL GRAVITATION?
2. WHAT TWO FACTORS DETERMINE THE FORCE OF GRAVITY BETWEEN TWO OBJECTS?
3. SUPPOSE THE MOON WERE CLOSER TO EARTH. HOW WOULD THE FORCE OF GRAVITY BETWEEN EARTH AND THE MOON BE DIFFERENT?
4. WHAT TWO FACTORS ACT TOGETHER TO KEEP EARTH IN ORBIT AROUND THE SUN?
5. WHY DOESN’T EARTH SIMPLY FALL INTO THE SUN?
6. HOW WOULD EARTH MOVE IF THE SUN (INCLUDING IT’S GRAVITY) SUDDENLY DISAPPEARED? EXPLAIN.