Transcript Gravity, Weight, Mass, Falling Objects, and Centripetal Force

Gravity, Weight, Mass,
Falling Objects, and
Centripetal Force
Law of Gravitation
Law of Gravitation
Any 2 masses exert an attractive
force on each other.
Force of gravity increases with
mass and decreases with distance.
Weight vs. Mass
Weight vs. Mass
Weight is the gravitational force
exerted on an object by the Earth.
Weight is a force, and mass is a
measure of the amount of matter an
object contains.
Your mass is the same no matter where
in the universe you are, but your weight
will vary because of gravity.
Calculating Weight
Weight is your mass multiplied by the
acceleration due to gravity (g) or 9.8
m/s2.
The formula for weight is:
weight = mass x g
Where g = 9.8 m/s2
Weight and Mass
Gravitation
Celestial Body Factor Relative
to Earth
Sun
Mercury
Venus
Earth
Moon
Mars
Jupiter
Saturn
Uranus
Neptune
Pluto
27.9
0.38
0.91
1
0.17
0.38
2.54
1.08
0.91
1.19
0.06
Falling Objects
Air Resistance
• The air resistance of an object depends
on its size, shape, and speed.
• Air resistance and NOT the mass of an
object is why certain things fall more
quickly than others.
• In a vacuum, there is NO air resistance,
so all things fall at the same rate.
In a Vacuum
Exit Ticket
1. Why do you feel the force of attraction
between you and the Earth, but not between
you and your pencil?
2. What is the difference between weight and
mass?
3. What is a vacuum and how do objects fall
differently in a vacuum?
Projectile Motion
The path that an object takes when it is
thrown or shot through the air.
This path is due to Earth’s gravitational
pull and the object’s own inertia.
Projectile Motion
Terminal Velocity
As an object falls, it accelerates and its
speed increases as does the force of air
resistance.
The force of air resistance increases
until it cancels out the force of gravity.
When the forces are balanced, the
object no longer accelerates, so it
reaches a constant speed called its
terminal velocity.
Centripetal Force and g’s
Centripetal Force
Centripetal force is an unbalanced force
pushing or pulling an object towards the
center of a circle.
Centripetal acceleration is acceleration
towards the center of a curved or
circular path.
Centripetal Force examples
from physicsclassroom.com
As a car makes a turn, the As a bucket of water is tied
force of friction acting
to a string and spun in a
upon the turned wheels of
circle, the tension force
the car provides centripetal
acting upon the bucket
force required for circular
provides the centripetal
motion.
force required for circular
motion.
As the moon orbits the
Earth, the force of gravity
acting upon the moon
provides the centripetal
force required for circular
motion.
No centripetal force example from
physicsclassroom.com
Without a centripetal force, an object in
motion continues along a straight-line
path.
With a centripetal force, an object in
motion will be accelerated and change its
direction.
Weightlessness