1. What is Weightlessness? More About the Effects of Gravity! SPH3U

2. Weightlessness Think of astronauts floating in space? Think of astronauts floating in space? Is it because there is zero gravity (zero- G)? Is it because there is zero gravity (zero- G)? The difference between the pull of Earth’s gravity on someone on the surface compared with 100 miles up is about 5%. The difference between the pull of Earth’s gravity on someone on the surface compared with 100 miles up is about 5%. Weigh 100 lbs on Earth, weigh 95 lbs 100 miles up! Weigh 100 lbs on Earth, weigh 95 lbs 100 miles up! Why do astronauts float around? Why do astronauts float around?

3. Falling Elevator Answer: They’re in continuous free-fall! Answer: They’re in continuous free-fall! Huh? Huh? Imagine you’re in an elevator in a very tall building Imagine you’re in an elevator in a very tall building Cable breaks! Cable breaks! You’re falling/accelerating towards the ground at a slower rate than the elevator. You’re falling/accelerating towards the ground at a slower rate than the elevator. If you were standing on a bathroom scale, what would it read? If you were standing on a bathroom scale, what would it read?

4. Free-Fall When you’re in free-fall, you feel as though you are weightless. When you’re in free-fall, you feel as though you are weightless. The speed of the object determines the orbit (or lack of!) The speed of the object determines the orbit (or lack of!)

5. Astronauts in Space Constant free-fall (not lack of gravity) is the reason astronauts float around in space Constant free-fall (not lack of gravity) is the reason astronauts float around in space They are constantly falling towards the Earth’s surface as they orbit around the Earth They are constantly falling towards the Earth’s surface as they orbit around the Earth But what keeps the space shuttle from free-falling to Earth's surface and crashing into it? But what keeps the space shuttle from free-falling to Earth's surface and crashing into it?

6. A spacecraft can maintain its free-fall for a very long period of time by traveling fast enough -- about 7.5 kilometres per second – horizontally. A spacecraft can maintain its free-fall for a very long period of time by traveling fast enough -- about 7.5 kilometres per second – horizontally. So that even though it is constantly being pulled toward Earth's surface, its free-fall path is parallel to the planet's curvature. So that even though it is constantly being pulled toward Earth's surface, its free-fall path is parallel to the planet's curvature.