Newton’s Law of Universal Gravitation Physics Dorsey Adapted from AP physics curriculum Tenafly HS, New Jersey Universial Gravitation.ppt
Universial Gravitation.ppt Isaac Newton Late 1600s, England Shouldn’t everything want to fall? Universial Gravitation.ppt
Universial Gravitation.ppt Questions If the planets are orbiting the sun , what force is keeping them in orbit? What force keeps the moon in its orbit? Could the force of gravity be universal? Universial Gravitation.ppt
Why does the moon not fall straight down onto the earth? Universial Gravitation.ppt
The Thought Experiment We have all thrown a ball. We know the harder you throw it level to the ground the further it goes. Universial Gravitation.ppt
The Thought Experiment If you keep throwing the ball at faster speeds, no air, it would go further. (watch this video) Universial Gravitation.ppt
The Thought Experiment If you keep throwing the ball at faster speeds, no air, it would go further. If it is shot fast enough, it keeps on going Even faster it gets shot away Picture from: http://www.astro.virginia.edu/class/oconnell/astr1210/guide08.html Universial Gravitation.ppt
Newton’s Law of Universal Gravitation Any two objects attract each other with a gravitational force, proportional to the product of their masses and inversely proportional to the square of the distance between them. The force acts in the direction of the line connecting the centers of the masses. Universial Gravitation.ppt
Newton’s Law of Universal Gravitation Universial Gravitation.ppt http://scienceblogs.com/startswithabang/upload/2009/07/meet_our_second_moon/400px-NewtonsLawOfUniversalGravitation.svg.png
Universial Gravitation.ppt Henry Cavendish’s experiment determined the proportionality constant G in 1798. Universial Gravitation.ppt http://www.newscientist.com/data/images/archive/1639/16390101.jpg
Universial Gravitation.ppt The Value of G. G= 6.67 x 10-11 N m2 / kg2 Universial Gravitation.ppt
Change of Gravitational Force with Distance Law of universal gravitation is known as an inverse square law. Universial Gravitation.ppt
Universial Gravitation.ppt Problem 1 Two spheres of mass 35kg are 60m apart. What force does one exert on the other? If the mass of on is tripled and the radius is quadrupled how does the force change? Universial Gravitation.ppt
Universial Gravitation.ppt Problem 1 Universial Gravitation.ppt
Universial Gravitation.ppt Problem 1 cont. Universial Gravitation.ppt
Universial Gravitation.ppt Problem 1 cont. Universial Gravitation.ppt
Universial Gravitation.ppt Problem 1 cont. Universial Gravitation.ppt
Universial Gravitation.ppt Problem 1 cont. Universial Gravitation.ppt
Universial Gravitation.ppt Problem 1 cont. Universial Gravitation.ppt
Universial Gravitation.ppt Problem 2 Two spheres of equal mass have a force of gravity of 7.0x10-9 exerted on each other. Find their mass if the distance between them is 7.0m. Universial Gravitation.ppt
Universial Gravitation.ppt Problem 2 Universial Gravitation.ppt
Universial Gravitation.ppt Problem 3 Find the value of the gravitational acceleration g. The mass of the earth is 6.0 x 1024kg. Universial Gravitation.ppt
Universial Gravitation.ppt Problem 3 cont Universial Gravitation.ppt
Universial Gravitation.ppt Problem 3 cont Universial Gravitation.ppt
Acceleration of Gravity Universial Gravitation.ppt
Universial Gravitation.ppt Watch this Video Universial Gravitation.ppt
Gravity’s Potential Energy Universial Gravitation.ppt
Gravity’s Potential Energy Universial Gravitation.ppt
Gravity’s Potential Energy Universial Gravitation.ppt
Potential Energy Practice The moon magically stops orbiting the earth and starts to fall in. Radius of average lunar orbit = r = 3.8E5 km mearth= 5.97E24 kg mmoon = 7.35E22 kg A) How much energy does the moon have? B) What would it’s speed be relative to the earth when it collides? (treat both as point masses) Universial Gravitation.ppt
Potential Energy Practice Universial Gravitation.ppt
Potential Energy Practice U = -7.7E28 J mmoon = 7.35E22 kg (the (-) means it would come toward the earth) B) What would it’s speed be relative to the earth when it collides? KE=change in PE If it hits the earth it lost all it’s distance so ½*mmoon*v^2= U v=sqrt(2U/mmoon) v=1448 m/s = 1.5 km/s Universial Gravitation.ppt