# AP Physics 1 review of Centripetal Forces | Physics | Khan Academy | Summary and Q&A

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July 29, 2016
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AP Physics 1 review of Centripetal Forces | Physics | Khan Academy

## TL;DR

Learn about the concepts of period, frequency, centripetal acceleration, centripetal forces, and gravity and their relationships in circular motion and orbits.

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### Q: What is the difference between period and frequency?

Period is the time it takes for a process to complete one cycle, while frequency is the number of cycles completed in one second. They are inversely related, with the period being equal to one over the frequency, and the frequency being equal to one over the period.

### Q: How is centripetal acceleration different from tangential acceleration?

Centripetal acceleration is the acceleration that changes the direction of an object's velocity in circular motion, always pointing towards the center of the circle. Tangential acceleration, on the other hand, changes the magnitude or speed of the object's velocity.

### Q: What are some examples of centripetal forces in everyday situations?

Gravity is a common centripetal force, such as the force that keeps the moon in orbit around the Earth. Other examples include tension in a yo-yo string, normal force in a loopty loop, and static frictional force for a car going around a roundabout.

### Q: How does force influence the direction of centripetal acceleration?

If a force is directed radially inward towards the center of the circle, it is considered a positive force and will contribute to the centripetal acceleration. If a force points radially outward, it is considered a negative force. Tangential forces do not contribute to the centripetal acceleration.

## Summary & Key Takeaways

• Period is the time it takes for a process to complete one cycle, while frequency is the number of cycles completed in one second.

• Centripetal acceleration is the acceleration that causes an object to move in a circular path, always pointing towards the center of the circle.

• Centripetal forces are forces that point towards the center of the circle, causing an object to move in a circular path.

• Gravity, described by Newton's universal law of gravity, is the force of attraction between masses and can be expressed as the product of the masses divided by the square of the distance between them.