forces - mr. finke's science class - home€¦ · lifting a ping pong ball . straw suck ! 9...
TRANSCRIPT
FORCES
Is gravity real - or does the Earth just suck?
2
What do forces do?
Make things ----
move
move faster
move slower
change direction
also
change shape
3
Big and Little forces
We can measure forces
Using a forcemeter
4
Sir Isaac
Newton
5
Which fruit ?
6
Newton?
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Now a game!
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Lifting a ping pong ball
.
straw
Suck !
9
ping pong ball falling
The arrow represents the force of gravity
10
The ball does not fall when your
sucking force = force of gravity
straw
Suck
gravity
How have I shown this ?
11
Which diagram shows the sucking
force equal to the force of gravity?
straw
Suck
gravity
straw
Suck
gravity
straw
Suck
gravity
Newton
metric unit of force
What is gravity?
Sir Isaac Newton
1642 – 1727
The Principia
Gravity
force of attraction between all objects in
the universe
Gravity
the larger an object’s mass, the greater
the gravitational force
Gravity
the greater the distance between two
objects, the smaller the gravitational force
the force of gravity decreases by the amount
equal to one divided by the distance (d)
squared
1/d2
17
The ball does not fall when your
upward force = force of gravity
straw
Suck
gravity
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Gravity down under
People do not fall off the Earth
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two objects dropped at the same time
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On the Moon – Apollo 15
http://nssdc.gsfc.nasa.gov/planetary/image/featherdrop_sound.mov
A heavy geological hammer and a falcon feather were dropped from the same height.
They hit the lunar surface at the same time.
astronaut David Scott
NASA pictures
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Hippo jump
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Hippo jump
Force of gravity
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Saved?
24
Hippo is still falling quickly
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Hippo is still falling quickly but not getting faster
How do we know?
Force of gravity
air resistance
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How can we slow Hippo down?
What can you change?
Air Pressure
air pressure is caused by the motion of
particles in the air
you do not feel the weight of the air
because the pressure inside your body is
equal to the air pressure around you
Air Pressure
air pressure changes with altitude
the higher you are, the lower the air pressure
Air Pressure
Barometer
instrument used to measure air pressure
30
Launching a satellite
The cannon ball must move very quickly to orbit the earth.
The Moon
orbits the Earth
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The Moon
The Earth
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The Moon
The Earth
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On the Moon
NASA pictures
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Very heavy boots- Why?
Answers? No gravity on the Moon Weightless on the Moon To stop them floating away They weigh very much less than on Earth To stop huge bounces The Moon’s gravity is very much less than the
Earth’s gravity
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Weightless?
or are they?
(NASA pictures)
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apparently weightless (pictures or animation only –not a demonstration)
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GRAVITY
Things fall
Things have weight
Things stay in place
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No Gravity Would an apple fall? Would things stay on earth? What would happen?
What? Why? How?
keep asking questions -like Newton !