Transcript Gravity - BotsRule

Gravity
• Gravity is the force that pulls objects toward
the center of the earth.
Gravity
• But…it goes beyond just that…….
Gravity
• Newton’s greatest discovery!
• The Law of Universal Gravitation.
– Every mass attracts every other mass with a
force that is proportional to the product of the
two interacting masses
– Force ~ (mass1 x mass2) / distance2
– Force decreases with the inverse square of
distance
Gravity
• Free fall is when the only force acting on an
object is gravity.
• All objects in free fall accelerate at the same
rate regardless of mass
• Demos
Gravity
• Fluid friction in the air is called “Air
Resistance”
• In air, an object in free fall will continue to
accelerate until the force of air resistance
equals the force applied due to gravity.
• The greatest velocity of a free fall object in
air is called “Terminal Velocity”
Gravity
• Weight is the measure of the force of
gravity on an object.
• Mass is a measure of the amount of matter
in that object
Gravity
• Weight is expressed with the equation:
• Newtons(N) = mass x acceleration due to
gravity.
• 1N = 1Kg x 1 m/sec2
• 9.8N = 1Kg x 9.8m/sec2
Gravity
• Example:
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A 100Kg person weighs……..
(N) = mass x acceleration due to gravity
100kg x 9.8m/s2
So…….a 100Kg person weighs 980N on the
Earth’s surface
Gravity
• Potential Energy is the energy an object has
because of it’s position in a force field, such
as a gravitational field.
Gravity
• Gravitational Potential Energy (GPE)=
Weight x Height
• GPE is expressed as Newton Meters Nm.
Gravity
• Since we know that weight = mass x
acceleration due to gravity.
• Logically……..
• GPE = mgh (mass x Acceleration due to
gravity x height)
• Demo..penny shot
Gravity
• As an object falls, it’s GPE turns into……
• Kinetic Energy, the Energy of motion
• Kinetic Energy(KE) = 1/2 mass x velocity2
• KE = 1/2mv2
Not really Gravity….Oh well!
• Momentum is the product of a objects mass
and its velocity.
• Momentum = Mass x velocity
Not really Gravity….Oh well!
• Conservation of Momentum
– The total momentum of any group of objects
remains the same unless outside forces act on
the objects.