Forces - I Love Physics Forever!
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Transcript Forces - I Love Physics Forever!
Forces
Types of Forces
Effects of Forces
Gravity, Mass and Weight
Newton’s Laws
Freefall
What is force?
Common symbol: F
Unit: Newton, N
Equivalent base units: kg-m-s-2
Types of Forces
Contact Force
Push
Pull
Friction
Tension
Normal Force
Upthrust
Bouyancy
Lift
Drag
Resistance
Thrust
Engine
Non-contact Force
Gravitational Force
Weight
Electrical Force
Magnetic Force
Types of Forces: Contact Force
Tension
pull
Friction
Normal Force
Types of Forces: Contact Force
Upthrust
Drag
Types of Forces: Contact Force
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Thrust
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Thrust
Types of Forces: Contact Forces
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Thrust
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Lift
Types of Forces: Non-Contact Forces
Weight
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Thrust
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Weight
Types of Forces: Non-Contact Forces
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Electrical Force
Magnetic Force
Mass versus Weight
Mass
Amount of matter in an
object
unit: kilogram, kg
Does not change with
location
Weight
Gravitational force on
the object
Unit: Newton, N
Equal to
Mass x acceleration
due to gravity
m x g
Where g = 10 ms-2
Changes with location
On earth, always acting
downward
Weight
Normal force
Weight
Air resistance
Weight
Drag
Friction
Thrust
Normal Force
Weight
Drag
Thrust
Upthrust
Effects of Forces
Change shape
Rigid bodies
Change the state of motion
Move from rest
Speed up
Slow down
Stop
Change its direction
Newton’s Laws
Change of Shape
extension
Who is Isaac Newton?
“Nature and Nature's laws lay hid in night:
God said, Let Newton be! and all was
light.”
Newton’s Third Law
For every action
there is an equal
and opposite
reaction
Law of Action and Reaction
Action and Reaction Forces
Action and Reaction Forces
Newton’s First Law
If no unbalanced
force acts on a
body then the
body is in
equilibrium.
Law of Inertia
What is Inertia?
The tendency of a body to resist changes in
its state of motion.
It is measured in terms of mass of a body.
When the forces are balanced
The body does not move,or
The body moves
At a constant speed
In the same direction
Balanced forces
Balanced Forces
The book stays still!
Balanced Forces
The airplane moves forwards at constant speed!
Balanced Forces
Drag
Thrust
Friction
The car moves at constant speed!
Your Turn!
Question #1, page 104
Newton’s Second Law
An unbalanced force changes the motion
of an object.
It speeds up
Or slows down
Or changes direction
Or changes speed and direction
Acceleration
change in motion
Equation
a =
force
mass
Unbalanced Forces
The car moves from rest.
The car speeds up.
Unbalanced Forces
The car slows down to stop.
The car slows down.
The Physics of Falling
The Physics of Falling
Freefall
Motion where only gravity is acting on the body
Air resistance is negligible
As the body falls, its
Speed increases
Acceleration is constant
Acceleration = g
The Physics of Skydiving
The Physics of Falling with Air Resistance
Air resistance increases with speed
Terminal Velocity
The maximum speed of a falling object
When upward forces balance downward forces
on the object
The End