Real-world examples of gravity keeping planets in orbit

📚 Quick Study Guide

• 🍎 Gravity is a force of attraction between objects with mass.
• ⚖️ The strength of gravity depends on the masses of the objects and the distance between them.
• 🌍 Planets orbit stars (like our Sun) because of gravity. The star's gravity pulls the planet towards it, while the planet's velocity keeps it from falling directly into the star.
• 📐 The orbit shape is an ellipse, not a perfect circle.
• ⏱️ Kepler's Laws of Planetary Motion describe these orbits mathematically.
• ⚗️ Newton's Law of Universal Gravitation: $F = G \frac{m_1 m_2}{r^2}$, where $F$ is the gravitational force, $G$ is the gravitational constant, $m_1$ and $m_2$ are the masses of the two objects, and $r$ is the distance between their centers.

🧪 Practice Quiz

1. Which force is primarily responsible for keeping planets in orbit around a star?
   1. Electromagnetic Force
   2. Strong Nuclear Force
   3. Weak Nuclear Force
   4. Gravitational Force
2. According to Newton's Law of Universal Gravitation, how does increasing the distance between two objects affect the gravitational force between them?
   1. Increases the gravitational force
   2. Decreases the gravitational force
   3. Does not affect the gravitational force
   4. Doubles the gravitational force
3. What shape are planetary orbits, as described by Kepler's Laws?
   1. Perfect Circle
   2. Square
   3. Ellipse
   4. Spiral
4. If a planet suddenly doubled in mass, how would the gravitational force between it and its star change?
   1. Halve
   2. Double
   3. Quadruple
   4. Remain the same
5. Which of the following factors does NOT affect the gravitational force between two objects?
   1. The mass of the first object
   2. The color of the first object
   3. The distance between the objects
   4. The mass of the second object
6. What happens to a planet's orbital speed when it is closer to its star?
   1. It slows down
   2. It speeds up
   3. It remains constant
   4. It stops
7. Which constant appears in the formula for Newton's Law of Universal Gravitation?
   1. Planck's Constant
   2. Speed of Light
   3. Gravitational Constant
   4. Boltzmann Constant