Mass vs Weight

Mass = the amount of matter in an object Matter = the substance that all physical objects are made of Matter is anything that has mass and takes up space Mass = the amount of matter in an object

Mass Finding the mass is equivalent to counting the number of atoms (amount of matter) something is made of

Mass We can’t really count atoms, instead we compare objects by using a balance If a bowling ball has a mass of 1000g, that’s like saying it has the same number of atoms as 1000g of water or 1000g of gold or 1000g of chips!

Isaac Newton 1642 – 1727

Not only does each atom have mass, it also has inertia Inertia = a resistance to a change in motion

A moving bowling ball will just keep going until some force stops it Mass A bowling ball will stay in one place forever, until some force pushes or pulls it. A moving bowling ball will just keep going until some force stops it

Mass A bowling ball has more atoms A bowling ball has more inertia Would you rather have a catch with a bowling ball or a soccer ball? A bowling ball has more atoms A bowling ball has more inertia A bowling ball is harder to throw and to catch

Isaac Newton 1642 – 1727

What strange force makes an apple (or anything else) fall from a tree? GRAVITY

Newton theorized that all matter has gravity An invisible force that attracts all matter to all other matter

What determines the amount of gravity?

mass = the amount of atoms in an object What determines the amount of gravity? If every atom has gravity, then more atoms means more gravity mass = the amount of atoms in an object

What determines the amount of gravity? Which has more mass, an apple or a chimp? Which has more mass, the apple or the Earth? Which has more gravity between them, an apple and a chimp or the apple and the Earth?

What determines the amount of gravity? Which has more mass, the Earth or the Sun? Which has more gravity between them, an apple and the Earth or an apple and the sun? The Sun obviously has more mass and more gravity, then how can the Earth pull harder? There must be more than just mass involved!

What determines the amount of gravity? Newton decided that the farther away you get, the weaker gravity becomes.

What determines the amount of gravity? Mass Distance

What determines the amount of gravity? Newton actually found a way to quantify the amount of gravity

Law of gravity

Law of gravity Notice you need the mass of BOTH objects ALSO – it is the distance between objects, NOT the distance from the Earth Notice it is distance SQUARED. 2x the distance = 4x weaker gravity 3x the distance = 9x weaker gravity 10x the distance = 100x weaker gravity

What would gravity be like on the moon? Gravity depends on the mass and the distance between objects. Say you weigh 120 lbs on Earth, then travel to the moon. The Moon is approximately 1/6 of the mass of the Earth. (Would your mass change?)

Things DO NOT float on the moon! What would gravity be like on the moon? 1/6 the mass will mean 1/6 the gravity!!!! Things DO NOT float on the moon! Things weigh 6x less and fall 6x slower! The Moon is approximately 1/6 of the mass of the Earth.

MASS = the amount of atoms Weight = the amount of gravity So what is the actual difference between mass and weight? MASS = the amount of atoms Weight = the amount of gravity On the moon Mass is the same, weight 6x less

Flying in an airplane Mass is the same, gravity is slightly weaker So what is the actual difference between mass and weight? Deep in a coal mine Mass is the same, gravity is slightly larger Flying in an airplane Mass is the same, gravity is slightly weaker

Mars is about 80% the mass of Earth. What would you weigh on Mars?

Explain this !!!!

A spring scale is used to measure weight PAY ATTENTION to the pointer when you zero the scale!

Universal Gravitational constant 6.67 x 10-11 m3 kg-1 s-2 OR .0000000000667 m3 kg s2