<img src="https://d5nxst8fruw4z.cloudfront.net/atrk.gif?account=iA1Pi1a8Dy00ym" style="display:none" height="1" width="1" alt="" />

# Gravity

## A force of attraction between things that have mass and how it relates to weight.

Estimated3 minsto complete
%
Progress
Practice Gravity

MEMORY METER
This indicates how strong in your memory this concept is
Progress
Estimated3 minsto complete
%
Physics of Free Fall

### Physics of Free Fall

Credit: US Navy
Source: http://commons.wikimedia.org/wiki/File:US_Navy_110625-N-DB458-127_Marines_jump_from_an_H-53_Sea_Stallion_helicopter_during_a_routine_sky_diving_evolution.jpg

These marines are in free fall until they open their parachutes. They are speeding toward Earth because of gravity.

#### The Back Story

• Being in free fall makes you feel weightless. But why would you feel weightless when you’re being pulled by Earth’s gravity? After all, weight is defined as the force of gravity pulling you toward Earth.
• True weightlessness occurs only in the absence of gravity. However, feeling weightless is something else. In free fall, you only feel weightless.
• Credit: Rod Herrea
Source: http://www.flickr.com/photos/herrea/4554946026/

You can experience freefall and weightlessness in a plane that is descending very quickly [Figure2]

• What is it like to feel weightless? This video clip from a free-fall wedding shows what it’s like:

#### Can You Apply It?

1. What is free fall? Give an example.
2. What gives you your sense of weight?
3. Why do you feel weightless during free fall?
4. Are astronauts in the International Space Station weightless or do they just feel that way? Explain.
5. What could you do in free fall that you couldn’t do otherwise?

### Notes/Highlights Having trouble? Report an issue.

Color Highlighted Text Notes