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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
