Newton’s Laws of Universal Gravitation

Newton’s law of universal gravitation Where: Fg = magnitude of the force of gravity (in N) G = 6.67 X 10-11 N• m2/kg2 M = mass of one object (in kg) m = mass of other object (in kg) r = distance between centres of masses (in m)

What is gravity? Isaac Newton would say: “A Force of attraction between two objects having mass anywhere in the universe”

What is gravity? Albert Einstein would say: “Mass curves space-time. This space-time distortion causes objects to fall towards a heavier mass because the heavier mass has resulted to a greater curvature of space-time” https://www.youtube.com/watch?v=jlTVIMOix3I

Big ‘G’ – 6.67 x 10-11 Nm2/kg2 What is Gravity? https://www.youtube.com/watch?v=Efh4bu4rcbs Read: 1) http://www.haydenplanetarium.org/tyson/read/2005/09/01/the-importance-of-being-constant 2) http://www.scientificamerican.com/article/puzzling-measurement-of-big-g-gravitational-constant-ignites-debate-slide-show/ Provide a brief description of how Cavendish measured Big G!

Example # 1 A spacecraft with a mass of 3.00 X 104 kg is 5000 km from the surface of the Earth. The mass of the Earth is 5.98 X 1024 kg and its radius is 6.38 X 106 m. What is the force of gravity acting on the spacecraft?

Example # 2 A spaceship has a magnitude of gravitational force of 1.00 X 102 N on the surface of some planet. If the spaceship moves to a distance of 1.5 times the radius of the planet, from the surface of the planet; determine the magnitude of the gravitational force.

Example # 3 A satellite is launched from the surface of Earth. If the satellite loses half of it’s mass on the way into orbit at a radius of 3 times the radius of the Earth. What will the relationship be between force of gravity on Earth and in orbit?

Example # 3 Find the distance in terms of rE, from the surface of Earth, of a 2000 kg spaceship that has a Fg of 970 N.