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

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!

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!!!)

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!

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!

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

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

Compare: Mass vs. Weight on different planets: Person on Earth is 150 lbs! Same person on Jupiter is 354.6 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?

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…

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?

Acceleration Rate of the Earth What is the acceleration of this interval? 1sec – 9.8m @ 9.8 m/s 2sec – 19.6m @ 19.6 m/s 3sec – 44.1m @ 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

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?

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

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

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?

Class Activity Gravity and Weight Lab

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

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