Ppt Gravity
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Ppt Gravity






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    Ppt Gravity Ppt Gravity Presentation Transcript

    • The Law of Gravitation
      • You exert an attractive force on everything around you and everything is exerting an attractive force on you.
      • This attractive force is called gravity.
      • Anything that has mass is attracted by the force of gravity.
      • The Law of Gravitation states that any two masses exert an attractive force on each other.
    • The Law of Gravitation
      • Gravitation force depends on two things:
        • The mass of the two objects
        • The distance between the two objects
      • Why do you suppose the Earth exerts a force on you that you can feel, but you can’t feel the force the desk is exerting on you?
    • Gravity – a basic force
      • There are four basic forces:
        • Gravity
        • Electromagnetic force
        • Nuclear force = Strong
        • Nuclear force = Weak
      Apply to an atom only Caused by electricity and magnetism
    • Gravitational Acceleration
      • When objects fall, the gravitational pull is 9.8 m/s 2
      • When a falling object is only affected by gravity it is said to be in free fall.
    • Gravitational Acceleration
      • If you drop a bowling ball and a marble off a bridge, which would hit the water first?
      • Things to consider…
    • Gravitational Acceleration
        • Force of gravity is greater on the bowling ball because of its larger mass.
        • The larger mass means it has a larger inertia so more force is needed to change its velocity.
        • Gravitational force on the marble is smaller because it has a smaller mass
        • The inertia on the marble is less and less force is needed to change the velocity.
        • Therefore, all objects fall with the same acceleration!
    • Weight
      • Even if you are standing still and you have zero acceleration, the force of gravity is still present.
      • Weight is equal to the support force, which under normal circumstances is also equal to the force exerted on an object by gravity.
      • Capital W stands for weight.
      • F g = mass x (acceleration due to gravity)
    • Weight
      • Because the gravitational force is the same as the weight and the acceleration due to gravity, the equation can also be written as:
      • W = (m)(9.8 m/s 2 )
      • … if the object is being supported!
    • Weight & Mass
      • Weight and mass are not the same thing.
      • Weight is a force
      • Mass is a measure of the amount of matter an object contains.
      • The greater the weight, the greater the attraction between the object and Earth.
    • Weightlessness
      • To be nearly weightless, you would have to be far from the Earth.
      • Astronauts experience this feeling when they are in space.
      • Why does the space station spin?
    • Gravity Factors
      • The acceleration due to gravity is directly proportional to the mass of the objects and inversely related to the distance squared.
    • Inverse Square Law
      • When a quantity varies as the inverse square of its distance from its source.
    • Law of Universal Gravitation
      • Every object attracts every other object with a force that for any two objects is directly proportional to the mass of each object.
    • Universal Gravitation
      • To find the F g between any two objects in the universe.
      • G is the gravitational constant of proportionality
      • G = 6.67 x 10-11 N m 2 /kg 2
      • F = G m 1 m 2 /r 2