Newton’s Law of Universal Gravitation When an object falls to earth (an apple for example), what shape path does it appear to take and why? It is a common misconception that astronauts in orbit are weightless because they have flown high enough to escape the Earth's gravity. In fact, at an altitude of 400 kilometres (250 mi), equivalent to a typical orbit of the Space Shuttle, gravity is still nearly 90% as strong as at the Earth's surface. Weightlessness actually occurs because orbiting objects are in free-fall

Gravitation Every object with mass attracts every other object with mass. Newton realized that the force of attraction between two massive objects: Increases as the mass of the objects increases. Decreases as the distance between the objects increases.

Law of Universal Gravitation Mm r2 FG = G G = Gravitational Constant G = 6.67x10-11 N*m2/kg2 M1 and M2 = the mass of two bodies r = the distance between them

Law of Universal Gravitation It is an inverse-square law: If the distance doubles, the force drops to 1/4 If the distance triples, the force drops to 1/9 Distance increases by 10 = FG increasesb by100 Other principles that follow inverse square laws: Sound, light, electricity, magnetism and

Law of Universal Gravitation

What did you have to do differently to solve this problem? The Moon is attracted to the Earth. The mass of the Earth is 6.0x1024 kg and the mass of the Moon is 7.4x1022 kg. If the Earth and Moon are 345,000 km apart, what is the gravitational force between them? FG = GM1M2 / r2 FG = (6.67x10-11 Nm2/kg2) FG = 2.49x1020 N (6.0x1024 kg)(7.4x1022 kg) (3.45x108 m)2

Variations in Gravitational Field Strength Strongest in red Weakest in blue

Calculating g in the universe Fg= GMm r² mg= GMm g= GM

Calculating g in the universe 1) Using your new formula, calculate for acceleration due to gravity on Earth 2 warm-ups Ramifications of increased Fg1)strong 2) short “ decreased Fg 1) tall 2) bones/muscles not as strong/atrophy

Warm up