Mass vs Weight. Mass Matter = the substance that all physical objects are made of Mass = the amount...

Mass vs WeightMass vs Weight

MassMass

Matter = the substance that Matter = the substance that all physical objects are all physical objects are

made ofmade of

Mass = the amount of Mass = the amount of matter in an objectmatter in an object

Matter is anything that has Matter is anything that has mass and takes up spacemass and takes up space

MassMass

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

something is made ofsomething is made of

MassMass

We can’t really count We can’t really count atoms, instead we atoms, instead we

compare objects by compare objects by using a balanceusing a balance

If a bowling ball has a If a bowling ball has a mass of 1000g, that’s mass of 1000g, that’s like saying it has the like saying it has the

same number of atoms same number of atoms as 1000g of water or as 1000g of water or

1000g of gold or 1000g 1000g of gold or 1000g of chips!of chips!

Isaac NewtonIsaac Newton

1642 – 17271642 – 1727

MassMass

Not only does each atom Not only does each atom have mass, it also has have mass, it also has

inertiainertia

Inertia = a Inertia = a resistance to a resistance to a

change in change in motionmotion

MassMass

A bowling ball will stay in one place A bowling ball will stay in one place forever, until some force pushes or forever, until some force pushes or

pulls it.pulls it.

A moving bowling ball will A moving bowling ball will just keep going until some just keep going until some

force stops itforce stops it

MassMass

Would you rather have a catch with a Would you rather have a catch with a bowling ball or a soccer ball?bowling ball or a soccer ball?

A bowling ball has more atomsA bowling ball has more atoms

A bowling ball has more inertiaA bowling ball has more inertiaA bowling ball is harder to throw and to catchA bowling ball is harder to throw and to catch

Isaac NewtonIsaac Newton

1642 – 17271642 – 1727

What strange force What strange force makes an applemakes an apple

(or anything else) (or anything else) fall from a tree? fall from a tree?

GRAVITYGRAVITY

Newton theorized that all Newton theorized that all matter has gravitymatter has gravity

GRAVITYGRAVITYAn invisible force that An invisible force that attracts all matter to all attracts all matter to all

other matterother matter

What determines the amount of What determines the amount of gravity?gravity?

massmass = the amount of = the amount of atoms in an objectatoms in an object

What determines the amount of What determines the amount of gravity?gravity?

If every atom has gravity, then If every atom has gravity, then more atoms means more gravitymore atoms means more gravity

What determines the amount of What determines the amount of gravity?gravity?

Which has more mass, an apple or a chimp?Which has more mass, an apple or a chimp?

Which has more mass, the apple or the Earth?Which has more mass, the apple or the Earth?

Which has more gravity between them, an apple Which has more gravity between them, an apple and a chimp or the apple and the Earth?and a chimp or the apple and the Earth?

What determines the amount of What determines the amount of gravity?gravity?

Which has more mass, the Earth or the Sun?Which has more mass, the Earth or the Sun?

Which has more gravity between them, an apple Which has more gravity between them, an apple and the Earth or an apple and the sun?and the Earth or an apple and the sun?

The Sun obviously has more mass and more The Sun obviously has more mass and more gravity, then how can the Earth pull harder?gravity, then how can the Earth pull harder?

There must be more than just mass involved!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 What determines the amount of gravity?amount of gravity?

•MassMass

•DistanceDistance

What determines the What determines the amount of gravity?amount of gravity?

Newton actually found a way to Newton actually found a way to quantify the amount of gravityquantify the amount of gravity

Law of gravityLaw of gravity

Law of gravityLaw of gravity

Notice you need the mass of BOTH objects

Notice it is distance SQUARED.

2x the distance = 4x weaker gravity

3x the distance = 9x weaker gravity

10x the distance = 100x weaker gravity

ALSO – it is the ALSO – it is the distance between distance between objects, NOT the objects, NOT the distance from the distance from the

EarthEarth

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?)

What would gravity be like on the moon?

1/6 the mass will mean 1/6 the gravity!!!!

The Moon is approximately 1/6 of the mass of the Earth.

Things weigh 6x less and fall 6x slower!

Things DO NOT float on the

Things DO NOT float on the

moon!

moon!

So what is the actual difference between So what is the actual difference between mass and weight?mass and weight?

MASS = the amount of atomsMASS = the amount of atoms

Weight = the amount of gravityWeight = the amount of gravity

On the moon

Mass is the same, weight 6x less

So what is the actual difference between So what is the actual difference between mass and weight?mass and weight?

Deep in a coal mineDeep in a coal mineMass is the same, gravity is Mass is the same, gravity is

slightly largerslightly larger

Flying in an airplaneFlying in an airplaneMass is the same, gravity Mass is the same, gravity

is slightly weakeris slightly weaker

Mars is about Mars is about 80% the mass 80% the mass

of Earth.of Earth.

What would What would you weigh on you weigh on

Mars?Mars?

Explain this !!!!Explain this !!!!

A A spring scalespring scale is used to is used to measure measure weightweight

PAY ATTENTION to the pointer when you zero PAY ATTENTION to the pointer when you zero the scale!the scale!

Universal Gravitational constant

6.67 x 10-11 m3 kg-1 s-2

.0000000000667 m3

OR

kg s2