# GRAVITY: pages 403-410 GRAVITY IS EVERYWHERE!.

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GRAVITY: pages GRAVITY IS EVERYWHERE!

A. GRAVITY = The FORCE of ATTRACTION between ANY two objects All matter (anything that has mass) has gravity…but it’s only noticeable between massive objects (like planets…)

Ex: Earth vs. moon Mass of the objects
The size of this gravitational force depends on 2 factors: Mass of the objects 1. __________________________ *As mass increases, the force of gravity increases Ex: Earth vs. moon

Distance between the objects
2. _________________________________ *As distance between the two objects _________, the force of gravity _________. increases decreases This is why we’re stuck to the surface of the Earth instead of being pulled off towards the more-massive sun.

The moon has about a 70% effect on our tides. The sun has a 30% effect
The moon has about a 70% effect on our tides. The sun has a 30% effect. The sun’s gravity is stronger (179x stronger than the moon), but it’s far away.

The rotation (spinning) of the Earth creates the equatorial “bulge”
The Earth’s diameter at the equator is 27 miles more than the pole to pole diameter So at the poles you are closer to the center of the earth, so you weigh slightly more.

Law of Universal Gravitation
All objects in the universe attract each other through the force of gravity.

NECAP QUESTION 2009

Acceleration of free-falling objects
VELOCITY 1. All falling objects accelerate (change ____________) towards the _________ of the Earth due to __________ CENTER GRAVITY the acceleration of a falling object due to gravity (on Earth) = 9.8 m/s2 or 9.8 m/s/s

This means that the velocity of a freely-falling object __________ by ____ m/s for every _______ that passes (up to a certain point…) 9.8 INCREASES SECOND But…on Earth, not all falling objects hit the ground at the same time because of _____________ or _______________. air resistance FLUID FRICTION

On the moon…all objects hit the surface at the SAME time because there is no ____ on the moon. There IS GRAVITY. Gravity = ____ of Earth. AIR 1/6 Moon = 1.63 m/s/s

C. Terminal Velocity -shape -size -weight
The __________ speed that an object can have in freefall due to ___________________. MAXIMUM AIR RESISTANCE Terminal velocity changes depending on the object’s -shape -size -weight

As objects fall, _____________ increases until it balances the _______ of the object
FLUID FRICTION WEIGHT Therefore, a heavier object will accelerate for a _________ time period and have a __________ terminal velocity. GREATER GREATER

A flat sheet of paper falls slowly because of air resistance -it reaches its TERMINAL VELOCITY right away. Weight Air Resistance If placed on a magazine, the paper accelerates with the magazine. Since the magazine weighs more, it accelerates for a longer time period.

“DROPPED FROM A HIGH POINT…”
Golf Ball Ping pong Ball A ping pong ball reaches its terminal velocity first A golf ball continues to accelerate for a greater time period and has a greater terminal velocity- so it hits the ground first. Drag Weight

FALLING PENNIES

FALLING CATS -There are cats on record that have survived falls of over 32 stories (~320 feet). -They are more likely to die in falls less than 5 stories. HOW IS THIS POSSIBLE? -On average, cats reach their terminal velocity (60 mph) after falling about 5 stories. - Once reaching this velocity, they relax and spread out like a parachute, minimizing injuries.

D. Projectile Motion: CURVED
Motion that has two components (horizontal & vertical) that combine to form a __________ path CURVED The two motions DO NOT affect each other

Astronauts “float” when inside an orbiting spaceship because they are _______________!
in FREE FALL

PARABOLIC FLIGHTS…experience “weightlessness” as you free fall with a plane…..
only \$2,950 per person!

ZERO GRAVITY CLASSROOM…

E. Weight vs. Mass 1. MASS The amount of _________ in an object that _______ changes. Measured in ___ MATTER NEVER kg 2. WEIGHT The gravitational ________ that an object experiences because of its _______. FORCE MASS Varies (changes) by location

Weight is a FORCE. F = ______________
Mass x acceleration Mass= 60kg Mass= 60kg

Homework: KIM vocabulary strategy using the following terms: weight
mass free fall terminal velocity projectile motion