Chapter 13

Chapter 13

1. The falling apple

   • Newton understood inertia
     • This conept was first developed by Galileo
       • Objects will continue moving in a straight line unless an outside force acts on that object.
         • He realized that the moon had to feel a force towards the earth if in moved around it in a curve
           • Curved motion is accelerated motion
           • He realized that the moon was falling towards earth just like the apple

2. The falling moon

   • Newton concluded that the moon was falling around earth.
     • Hypothesized that the moon was a projectile moving around earth under the influence of gravity
   • Applied this newly found rule to all objects
     • Later invented calculus to explain the law of universal gravitation.
     • Everything attracts to everything. The attraction is realted to mass and distance.

3. Newton's law of universal gravitation

   • All objects attract all other objects that is directly porportional to mass and distance.
     • force=mass1*mass2/distance^2
     • force depends on distance and center of mass

4. Univerasal Gravitational Constant G

   • Describes strength of gravity

5. Inverse-Square Law

   • quanity varies as the inverse square of its distance
     • gravity decreases
       • force of gravity weakens as the square of the distance

6. gravitational field

   • earth has a gravitational field which interacts with causes objects to feel gravitational force
   • type of forcefield
     • magnetic forcefield
   • objects not in contact with earth are embedded in its gravitational field

7. Weight and Weightlessness

   • weight is force exerted against support
   • weightlessness occurs in absence of support force

8. Escaping Gravity

   • It is impossible to get away from an objects gravity since it covers an infinite distance
     • it is possible to move fast enough for the gravity to be unable to hold us back
       • this rate is escape velocity

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