We learned that all objects attract each other with a gravitational force. The earth and the moon attract each other, the earth and the sun attract each other, and so on. If that's the case, why doesn't the moon crash into the earth? Is there another force pushing the moon away from the earth?
Now that we've learned about gravity, uniform circular motion and centripetal force, let's take a look at something that combines these concepts: orbital motion.
An orbit is the circular or elliptical path of an object as it moves around another object, with only the force of gravity acting on it. The moon and thousands of satellites are in orbit around the earth, and the earth and the other planets are in orbit around the sun. Since gravity is the only force involved, we'll see how objects in orbit are really in projectile motion or free fall and have zero apparent weight.
If an orbit is a circle, gravity is the centripetal force causing the circular motion. That means we can combine the equations for gravitational force and centripetal force to find the object's orbital radius, speed and period.
We'll also take a look at Kepler's Laws of planetary motion. With the help of others, Johannes Kepler discovered that the orbit of a planet around the sun actually follows an ellipse instead of a circle. These laws can tell us even more about orbital motion.
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Free-Response Questions
Circular motion
Law of gravitation
- Orbits and Centripetal Force
- Kepler's Laws
We learned that all objects attract each other with a gravitational force. The earth and the moon attract each other, the earth and the sun attract each other, and so on. If that's the case, why doesn't the moon crash into the earth? Is there another force pushing the moon away from the earth?
Now that we've learned about gravity, uniform circular motion and centripetal force, let's take a look at something that combines these concepts: orbital motion.
An orbit is the circular or elliptical path of an object as it moves around another object, with only the force of gravity acting on it. The moon and thousands of satellites are in orbit around the earth, and the earth and the other planets are in orbit around the sun. Since gravity is the only force involved, we'll see how objects in orbit are really in projectile motion or free fall and have zero apparent weight.
If an orbit is a circle, gravity is the centripetal force causing the circular motion. That means we can combine the equations for gravitational force and centripetal force to find the object's orbital radius, speed and period.
We'll also take a look at Kepler's Laws of planetary motion. With the help of others, Johannes Kepler discovered that the orbit of a planet around the sun actually follows an ellipse instead of a circle. These laws can tell us even more about orbital motion.
1. Orbits and Centripetal Force
2. Kepler's Laws
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