Transcript force of acceleration - River Vale Public Schools

GRAVITY
GRAVITY
•a force of acceleration that causes objects to become
attracted to each other
-based on the object’s mass and distance
between them
•The acceleration due to gravity on Earth is
9.8 m/sec2 (~22 mph/sec)
(This means that each second an object falls,
it increases its speed by 9.8 m/sec until it
reaches its terminal velocity)
•Mass: Amount of matter in an object
•Weight: How heavy an object is because of
gravitational pull
•Gravity pulls all objects at the same rate.
•Mass does not affect the pull from gravity.
However….
Some objects do fall slower
because of
-A force that opposes the motion of
an object as it moves through air
Some objects also fall slower
because of their……
TERMINAL VELOCITY
•highest speed that an object can fall at
determined by the object’s shape and mass
Once an object reaches its terminal velocity,
it falls at a constant velocity.
(It does not accelerate unless its shape changes.)
Reaches this when the air resistance exerts an upward force exactly equal and
opposite to the force of gravity. Heavier mass needs faster falling speed for drag to
equal gravity
The elephant hits first because of its mass. It
takes more time to reach its terminal velocity.
The feather reaches its terminal velocity very quickly
because it has very little mass.
Vacuum: A vacuum is a place that has no matter –
thus there is no air (ex: in outer space)
If there is no air, there is no air resistance
All objects will fall at the same velocity
regardless of shape and mass.
Tennis ball test
A tennis ball’s terminal velocity
is about 70 mph.
…..but with air resistance and
outside factors, the speed should
be between 40-50 mph.
Other Terminal Velocities
Human ~120mph
Raindrop ~ 12mph
16lb Bowling Ball ~ 163mph
Baseball ~ 75mph
HOW WOULD OUR LIVES BE
DIFFERENT WITHOUT GRAVITY???
http://www.explorelearning.com/
Sign up for the gravity interactive – off
the leaning tower of pisa
Teacherdomain.org
Balloon Car Project due Friday
Poster
Data Tables (re-done on the computer)
•Distance
•Top Speed
•Momentum
Builders Journal (preferred typed)
Terms Sheet (typed)
UPCOMING SCIENCE EVENTS
Test on Thursday 22nd
Mini
Project
Next
Week
st
nd
1 or 2 Week in January
Science Placement Test from PV
LET’S REVIEW………..NEWTON’S LAWS
FIRST LAW
AN OBJECT IN MOTION WILL
STAY IN MOTION UNLESS
ANOTHER FORCE STOPS IT
AN OBJECT AT REST WILL
STAY AT REST UNLESS
ANOTHER FORCE STARTS IT
SECOND LAW
FORCE = MASS x ACCELERATION
“HEAVIER OBJECTS NEED
MORE FORCE TO GET THEM
GOING OR TO STOP THEM”
THIRD LAW
EVERY ACTION HAS AN EQUAL
AND OPPOSITE REACTION
CAR GOES
THIS WAY
AIR GOES
THIS WAY
YOUR BALLOON CAR WILL
EXPERIENCE ALL THREE
IT WILL NOT MOVE UNTIL YOU GIVE
IT A FORCE-IT WON’T STOP UNTIL
FRICTION OR A WALL STOPS IT.
THE HEAVIER YOUR CAR IS, THE
MORE FORCE IT WILL TAKE TO GET
IT GOING
WHEN THE AIR COMES OUT OF
THE BALLOON, YOUR CAR WILL
GO FORWARD (the opposite way)