1. The Difference between Mass & Weight
That’s heavy man. Heavy…

2. What we learned last time:
Gravity is dependant upon the mass of two objects and the distance between them.
If mass increases – Force of Gravity increases
If distance increases – Force of Gravity decreases.
Jupiter has more mass than Earth;
Therefore it has more gravity
The satellite is farther from the center of Earth than we are;
Therefore the planet is not pulling as hard on the satellite
as the person standing on the surface!

3. What is Weight?
Definition: Weight is a measurement of how strongly gravity pulls on a mass.
Weight is completely dependent on the amount of gravity there is.
It the result of the force of gravity!!!
Without gravity there is NO WEIGHT (the ultimate diet plan!!!)

4. Amount of Mass & Gravity = Weight
If you add more mass – you’ve increased the attractive force between you and the earth
Therefore you “weigh” more!
The Earth must really like me!

5. Gravity, Distance and Weight:
If I leave the earth and head to outer space, I am farther away from the gravity source.
Therefore, you weigh less.
Dude! I CAN FLOAT AROUND!

6. Mass ≠ Weight Mass and Weight are NOT the same thing!
Mass: Amount of matter an object contains
Has inertia (resistance to a push/pull)
Weight (Force):
Dependant upon Gravity (mass is not)
Attraction between two objects
Can change if the objects change distance or mass

7. Mass and Gravity = Weight
Weight really is a measurement of the gravitational attraction between you and the earth.
Remember – Weight is a force measurement
Mass and Gravity = Weight
When gravity pulls on your mass,
the resulting force is called “weight”!
Source of Gravity
Source of Gravity
Small mass = less pull = less weight
Large mass = more pull = more weight

8. Compare: Mass vs. Weight on different planets:
Person on Earth
is 150 lbs!
Same person on
Jupiter is lbs!!!
Why is this true? What is different
between Jupiter and Earth?
Jupiter has more mass than the Earth
Therefore it has more gravity! Your same
mass would weigh more on Jupiter than on Earth!
Q: Did the person’s MASS (amount
of matter that makes them
up) ever change?

9. Q: How does gravity accelerate an object?
How objects fall as a result of gravity was a matter of debate for scientific
thinkers as far back as ancient times!
A “philosopher” named Aristotle felt that heavier objects
(greater weight) would fall faster than lighter objects
when pulled by gravity… This idea was accepted for 100’s of years!
After many years (during the renaissance) a scientist
named Galileo had a different idea:
To try and prove his idea, he took cannon balls to the
top of the leaning tower of Pisa…
So what happened?
Well, let’s go see for
ourselves!
And then he dropped them!!!
He felt that all objects would fall at the same rate
no matter what the mass or weight was…

10. Test of Gravity
Which one fell faster – the heavier one or the lighter one?
Galileo found that no matter how large or small, the objects fell at the same Velocity.
So at what rate do objects accelerate due to Earth’s gravity?

11. Acceleration Rate of the Earth
What is the acceleration of this interval?
1sec – 9.8 m/s
2sec – 19.6 m/s
3sec – 29.4 m/s
What is the acceleration of this interval?
What is the acceleration of this interval?
Gravity’s Acceleration on the Earth = 9.8 m/s2

12. Wait a second! We already talked about how leaves and feathers
fall very slowly and even changes directions
So what makes the leaf and feather fall
differently than a cannon ball?
So will feathers and leaves always
fall slower than cannon balls?

13. Q: So what if we got rid of all the air?
Feather Drop in a Vacuum:
Q: So what if we got rid of all the air?
Galileo Experiment – Apollo 15
Hammer & Feather Experiment
Google Video

14. So how do we solve for weight?
Force = Mass x Acceleration
Acceleration Rate of Earth’s Gravitational Pull
Weight = Mass x Gravity Acceleration

15. Compare your weight on Earth to what is would be on the Moon:
Discuss: Why does your weight change?
Discuss: Does your mass change as well?

16. Class Activity
Gravity and Weight Lab

17. Notice that the weight has increased but the mass stays the same.
Changes in Mass???
1000kg 1N
Notice that the weight has increased but the mass stays the same.
0kg 0N
Mass Weight

18. Acceleration & Force Review
Rate at which things move faster or slower
Amount of matter (atoms) the object has.
Has Inertia – Resistance to change.
Push or Pull
Makes things with mass accelerate