# Gravity in the Solar System

## Gravity is the attraction of two objects that is dependent on their mass and distance from each other.

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Credit: Schaffhausen
Source: http://commons.wikimedia.org/wiki/File:Skyscraper.jpg

Imagine that you’re in an elevator on the top floor of a skyscraper. You press the down button and the doors close. What questions could you ask? How would you answer them scientifically?

#### Why It Matters

Questions can be scientific or nonscientific. A nonscientific question to ask in the elevator might be “how many angels are riding in the elevator with me?” Since humans cannot sense angels, there is no way to answer that question. A scientific question must be testable. A question is scientific if it can be answered using scientific method. People ask themselves scientific questions all the time. Sometimes they answer the question by looking up the answer. If there’s no answer they may develop a hypothesis. Then they will test the hypothesis to see if it’s valid. The best scientific questions are the ones that haven’t been answered yet.

#### Can You Apply It?

1. What are three main questions that are asked in this video?
2. What is Newton’s second law?
3. You are standing on a scale in the elevator and the elevator is stationary. What two forces are acting on the scale and what is their direction?
4. You’re standing on the scale and the elevator is accelerating downward. Does the scale read higher, lower or the same as if the elevator were stationary? Use Newton’s second law to explain your answer.

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