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Chapter 9: Circular MotionPowerPoint Presentation

Chapter 9: Circular Motion

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Chapter 9: Circular Motion

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Chapter 9: Circular Motion

- An axis is the straight line around which rotation takes place

- When an object turns about an internal axis.
- An axis located within the body of the object

- The motion is also called spin.
- Earth Rotates about its axis once every 24 hours.

- When an object turns about an external axis.
- Earth Revolves around the sun once every 365¼ days.

- What we simply called speed in Chapter 2.
- A distance moved per unit time.
- Linear speed varies based on radius of a circle.
- On the Merry-Go-Round, the horses on the outermost ring have to travel faster to keep up with the horses that are closer to the center axis.

- The speed of something moving along a circular path.
- We call it tangential motion because the speed is always tangent to the circle.
- We can use tangential speed and linear speed as the same thing for circular motion.

- The number of rotations per unit of time. Symbol (ω-omega)
- Sometimes called angular speed.
- All parts of the merry-go-round rotate about their axis in the same amount of time.
- Units for Rotational Speed = Rev. / second or Rev. / min.

- The record player rotates with a rotational speed of 72,000RPM.
- Tangential Speed = Radial dist x Rotational Speed
v= r ω

- Any force that causes an object to follow a circular path.
- Centripetal means “center seeking” or “toward the center.”
- The force that holds the occupants in a rotating ride.

- The Physics curse word!!!
- Very commonly misused.
- Means “center-fleeing” or “away from the center.”
- Misconception that centrifugal force pulls you outward during circular motion.
- Actual force is just the inertia of the body traveling tangent to the circle.

- As a ball is whirled above the head, it is the inertia of the ball that wants to continue moving in a straight line. Instead, the ball is forced inward to change its direction (Centripetal Force-supplied by string).

- When a wheel or apparatus is spun at just the right speed so that the acceleration feels like the gravity they are accustomed to.

- ac= v2/r
- Fc = (mv2)/r
- Vrotational = r ω = (2π r)/t