# Gravity and Orbital Mechanics - Physics 101 / AP Physics 1 Review with Dianna Cowern | Summary and Q&A

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October 29, 2020
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Physics Girl
Gravity and Orbital Mechanics - Physics 101 / AP Physics 1 Review with Dianna Cowern

## TL;DR

This video explains the concept of gravity and how it affects objects on Earth and in space, including the formation of orbits.

## Key Insights

• ๐ Gravity is a fundamental force that attracts objects with mass towards each other.
• ๐ฎ Newton's law of universal gravitation describes the force between two objects and is crucial for understanding planetary motion and orbital behavior.
• ๐ฐ๏ธ Orbital velocity is determined by the mass of the object being orbited and the distance from its center, and it enables objects to stay in orbit.
• ๐ป Kepler's Third Law allows for the calculation of the mass of celestial objects based on orbital periods and distances.
• ๐ The discovery of dark matter has revolutionized our understanding of the universe, and it constitutes a significant portion of its total mass.
• ๐ Einstein's theory of general relativity explains how gravity can bend light, providing a more precise model of gravitational effects compared to Newton's laws.

## Transcript

HOST: This is a candle inside of a completely closed box. We're about to drop it 11 meters and see what happens to the flame. Check it out--it becomes completely spherical. This maybe isn't surprising if you've ever seen pictures of candles in space. They become this eerie, spherical shape. But wait, why should a candle in space and a candle fallin... Read More

### Q: Why does an apple fall towards the ground even without any physical connection?

This is due to the force of gravity, which attracts objects with mass towards each other. The apple is being pulled towards the Earth's center by its gravitational field.

### Q: How did scientists determine the mass of the sun using orbital periods?

Scientists used Kepler's Third Law to relate the orbital period of a planet to its distance from the sun and the mass of the sun. By measuring the orbital period and distance of Earth, they were able to calculate the mass of the sun.

### Q: What is dark matter, and how was its existence inferred?

Dark matter is a type of matter that does not emit or reflect light, making it invisible. Its existence was inferred by observing the high orbital speeds of stars in galaxies, suggesting the presence of additional mass that cannot be accounted for by visible matter.

### Q: How does Einstein's theory of general relativity explain the bending of light in a gravitational field?

According to general relativity, massive objects bend and warp the fabric of spacetime, and light beams passing near these objects follow curved paths. This explains why light beams can be deflected by the gravitational field of massive objects.

## Summary & Key Takeaways

• The video introduces Newton's law of universal gravitation, which explains the force of gravity between objects with mass.

• It explores the history of how gravity was discovered and how it led to the understanding of planetary motion and orbital behavior.

• The video also discusses the calculation of orbital velocity and how it is related to the mass and radius of the object being orbited.