GRAVITY: Ch 12.

Sec. 2

pages

403-410GRAVITY 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…)

The size of this gravitational force depends on 2 factors:

1. __________________________Mass of the objects

*As mass increases, the force of gravity increases

Ex: Earth vs. moon

This is why we’re “stuck” to the surface of the Earth instead of being pulled off towards the more-massive sun.

2. _________________________________Distance between the objects

*As distance between the two objects _________, the force of gravity _________.increases decreases

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.

Spring tides: action of tides springing

out and back. (highest highs and

lowest lows)

Neap tides: Sun and moon are at

right angles to one another and tidal

influences partially cancel each other

out. (difference between high tide

and low tide is minimal)

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.

Poles @ sea level: 9.780 m/s2

Equator @ sea level: 9.832 m/s2

~0.5% more force

Law of Universal Gravitation• All objects in the universe attract each other

through the force of gravity.• As distance increases, force decreases.• As mass increases, force increases.

NECAP QUESTION

2009

B. Acceleration of free-falling objects

1. All falling objects accelerate (change ____________) towards the _________ of the Earth due to __________

• the acceleration of a falling object due to gravity (on Earth) =

9.8 m/s2 or 9.8 m/s/s

VELOCITYCENTER GRAVITY

•But…on Earth, not all falling objects hit the ground at the same time because of _____________ or _______________.

air resistanceFLUID FRICTION

•This means that the velocity of a freely-falling object __________ by ____ m/s for every _______ that passes (up to a certain point…)

INCREASES 9.8SECOND

Force of G on Moon = 1.63 m/s/s

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.

AIR1/6

Hammer & Feather Drop on Moon

(Apollo 15)

Water Balloon Fight in Space

C. Terminal Velocity

•The __________ speed that an object can have in freefall due to ___________________.

MAXIMUMAIR RESISTANCE

-shape

-size

-weight

•Terminal velocity changes depending on the object’s

• 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

Flying Squirrel Suits?!

AirResistance

Weight

A flat sheet of paper falls slowly because of air resistance -it reaches its TERMINAL VELOCITY right away.

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…”

Drag

Weight

GolfBall

PingpongBall-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.

- Falling Objects Lab!

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:

•The two motions DO NOT affect each other

• Motion that has two components (horizontal & vertical) that combine to form a __________ pathCURVED

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…

Zero Gravity!

E. Weight vs. Mass

1. MASS

•The amount of _________ in an object that _______ changes. Measured in ___

2. WEIGHT

•The gravitational ________ that an object experiences because of its _______.

•Varies (changes) by location

MATTERNEVER

FORCEMASS

kg

Weight is a FORCE. F = ______________

Mass= 60kg

Mass= 60kg

mass x acceleration

Homework:Homework:

KIM vocabulary strategy using the following terms:weightmassfree fallterminal velocityprojectile motion

KIM vocabulary strategy using the following terms:weightmassfree fallterminal velocityprojectile motion