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Gravitational Force

Gravitational Force. 4 Forces of the Universe. Nuclear : Strong forces holding the nucleus of an atom together (gluon) Weak : Forces as a result of some atoms that decay the nucleus ( radioactive ) Electromagnetic : a force based on electricity, magnetism and light properties

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Gravitational Force

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  1. Gravitational Force

  2. 4 Forces of the Universe • Nuclear : Strong forces holding the nucleus of an atom together (gluon) • Weak: Forces as a result of some atoms that decay the nucleus ( radioactive ) • Electromagnetic : a force based on electricity, magnetism and light properties • Gravitational: The weakest force caused by the 2 factors, MASS and DISTANCE

  3. Gravity vs. displacement Graph

  4. Henry Cavendish1731 - 1810 • Education.      At age 18, (1749) he entered Cambridge in St. Peter's College.  He left without graduating four years later.  His first paper Factitious Airs appeared 13 years later. • Eccentric in life.  Henry Cavendish had a peculiarly odd demeanor.  He was morbidly shy of women and strangers and avoided ever speaking to them.  Henry Cavendish was extremely wealthy, he became the single largest holder of bank stock in England.  

  5. Cavendish Experiments • Cavendish's most famous accomplishment in science took place during the years 1796 - 8 during which he established the mean density of the earth to be 5.448.  The current estimate is 5.5. Verification of G, Gravitational Constant • Hydrogen (Inflammable air). Cavendish is generally credited with the discovery of inflammable air  

  6. Universal Gravitation • The force on two objects vary inversely with the square of the distance between the objects. • F a 1 d2 • F = G m1 m2 where G =6.67 x 10 -11 Nm2/kg2 r2

  7. Mass, distance, force • How does the mass change the force of gravity? • How does distance change the force of gravity? • Mass has a direct change of the force. • Distance is an inverse square to the force.

  8. Gravitational Problem #1 • Gravitational force of attraction F exists between two point masses. Mass A distance is 3m and B is changed to only 1m, the gravitational attraction between the masses has changed by: • A Tripled F • B 1/9 F • C 9 times F • D no change in F 3m Mass A Mass B 1m Answer: 9 times the Force Mass A Mass B Mass B

  9. Gravitational Problem #2 • Gravitational force of attraction F exists between two point masses, mass A and B are separated by a fixed distance. After mass A is tripled and B remains the same, the gravitational attraction between the masses is: • A Tripled F • B 1/9 F • C 9 times F • D no change in F 3m Mass A Mass B 3m Mass A Mass B Answer: Tripled Force

  10. Gravitational Problem #3 • Gravitational force of attraction F exists between two point masses, mass A and B are separated by a fixed distance. After mass A is tripled and B is halved, the gravitational attraction between the masses is: • 1/6 F • 2/3 F • 3/2 F • 6 F 3m Mass A Mass B 3 m Mass B Answer 3/2 F Mass A

  11. Gravitational Problem #4 • Gravitational force of attraction F exists between two point masses. After the distance is doubled between A and B, the gravitational attraction between the masses is: • 2x F • 4x F • ½ F • ¼ F 3 m Mass A Mass A Mass B 6m Mass B Mass A Answer : ¼ F ( Inverse Square )

  12. Gravitational Problem #5 • Find the Force of attraction (gravity) between two 7.26 kg Bowling balls separated by .3 m. • F = G m1 m2 r2 • F = (6.67 x 10 -11 Nm2/kg2) ( 7.26kg)( 7.26kg) (0.30m)2 • F = 6.67 x 52.7076 x 10 -11 N m2 • .09 m2 • F = 351.559692 / .09 x 10 -11N • F = 3906.2188 x 10 -11N • F = 3.91 x 10 -8 N

  13. Einstein’s Gravity?? • “The editors of Scientific American have asked me to write about my recent work which has just been published. It is a mathematical investigation concerning the foundations of field physics” • He discussed his special and general theories of relativity and his work toward a unified field theory in a 1950 Scientific American article. At the time, he was not convinced that he had discovered a valid solution capable of extending his general theory of relativity to other forces. He died in 1955, leaving the problem of Gravity unsolved.

  14. Summary • Gravity is the weakest force • Gravity is only a force of attraction • Gravity is dependant on distance and mass • The force of gravity changes directly with the mass • The force changes inversely to the square of the distance

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