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GravityNewton rationalized that if the earth puts a forceon an apple, then who’s to say that it doesn’texert a force on th...
Gravity must beproportional to bothmasses because ofNewton’s 3rdLaw(Equal and oppositeforces)F α M mNewton’s Math ProofFor...
Law of Universal GravitationEvery particle in the universe attracts every otherparticle with a force that is proportional ...
Sample ProblemA 50 kg girl & a 70 kg boy are 50 cm apart on apark bench. Find the force of attraction…Field  Area around ...
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Ch4.5 - conceptual gravity

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Newton's Law of Universal Gravitation power point for conceptual physics students with little math background.

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Ch4.5 - conceptual gravity

  1. 1. GravityNewton rationalized that if the earth puts a forceon an apple, then who’s to say that it doesn’texert a force on the moon?Contact vs. Non-contact Forces↓  Newer concept: forceMust be touching acting at a distance(gravity, magnets,electricity…)
  2. 2. Gravity must beproportional to bothmasses because ofNewton’s 3rdLaw(Equal and oppositeforces)F α M mNewton’s Math ProofForce of gravity mustdecrease by theinverse square of thedistance.F α 1/r2This is known as theinverse square law!It is repeated inelectricity andmagnetism!CombineThese!2MmFrα 2GMmFr=
  3. 3. Law of Universal GravitationEvery particle in the universe attracts every otherparticle with a force that is proportional to theproduct of their masses and inverselyproportional to the square of the distancesbetween them. This force acts along a linejoining the 2 particles.2GMmFr=G = gravitational constant (small or large?)G = 6.67 x 10-11Nm2/kg2It took 100 years later for this law to be proven.Henry Cavendish performed the experiment.
  4. 4. Sample ProblemA 50 kg girl & a 70 kg boy are 50 cm apart on apark bench. Find the force of attraction…Field  Area around anobject that affectsother objects.Gravitational Field Area around amass that affectsother massesWhat represents thegravitational field around theearth?At Crown Point, the radiusof the Earth is 6.37101 x106m. If the Earth has amass of 5.98 x 1024kg.Then calculate the Earth’sgravitational field in CrownPoint.11 242 6 226.67 10 (5.98 10 )(6.37101 10 )9.83 /GM x xgr xg m s−= ==

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