2.2.3 Uniform Circular Motion

Uniform Circular Motion

​Objects traveling in circular motion have constant speed and constantly CHANGING velocity – changing in direction but not magnitude

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​v=d/t

​the 'd' in this case is

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​the 't' in this case is

Multiple Choice

A tennis ball on a string is spun clockwise around a circle. After the string breaks, which path will the tennis ball follow?

• Path I

• Path II

• Path III

• Path IV

Multiple Choice

•A student on an amusement park ride moves in a circular path with a radius 3.5 m once every 8.9s. The student moves at an average speed of

• 0.39 m/s

• 1.2 m/s

• 2.5 m/s

• 4.3 m/s

​Centripetal Force

​•Inertia causes objects to travel STRAIGHT

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•Paths can be bent by FORCES

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•CENTRIPETAL FORCE bends an object’s path into a circle - pulling toward the CENTER

​Misconception

​The doors to the “Gravitron” close and it starts to spin. 

You are pushed against the outside edge of the ride and

pinned there,  You must be experiencing “centrifugal

force” throwing you outward from the ride!  Right?

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https://www.youtube.com/watch?v=UMvtizOAtVU

​Head to ppt for slide 5

​What is the sensation that you feel?

​•centrifugal (center fleeing) force

–A ‘fictitious’ or ‘inertial’ force that is experienced from INSIDE a circular motion system – WHAT YOU FEEL

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•centripetal (center seeking) force

–A true force that pushes or pulls an object toward the center of a circular path – WHAT ACTUALLY HAPPENS

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​https://www.youtube.com/watch?v=LPg9Tm4L9nk

Multiple Choice

Is the centrifugal force a real force acting on your body in the gravitron?

• Yes, you are pushed outwards from the center

• No, it just feels like you are being pushed out, but no force is actually pushing you outwards

• Maybe...

• Bigfoot is always the answer

Multiple Choice

A body, B, is moving at constant speed in a horizontal circular path around point P. Which diagram shows the direction of the velocity (v) and the direction of the centripetal force (Fc) acting on the body?

• 1

• 2

• 3

• 4

​Centripetal Acceleration

​•Centripetal force is a NET FORCE

•Causes ACCELERATION

•In the SAME DIRECTION AS NET FORCE

Multiple Choice

•What is the centripetal acceleration of a toy ball on the end of a 1.44 meter long string if it is moving at 12 meters per second?

• 0.12 m/s^2

• 8.33 m/s^2

• 0.173 m/s^2

• 100 m/s^2

​If you substitute in for centripetal acceleration you can create a new equation for centripetal force. This is not on your reference table!

Multiple Choice

•What is the centripetal acceleration acting on a 2000 kilogram airplane if it turns with a radius of 1000 meters while moving at 300 meters per second?

• 180,000 m/s^2

• 0.3 m/s^2

• 90 m/s^2

• 600 m/s^2

Multiple Choice

•What is the centripetal force acting on a 2000 kilogram airplane if it turns with a radius of 1000 meters while moving at 300 meters per second?

• 90000N

• 600N

• $$1.8x10^5N$$  

• $$1.77x10^6N$$  

Multiple Choice

•Is it possible for a 1000 kilogram car to make a turn with a radius of 50 meters while moving at 15 meters per second with rubber tires on dry asphalt?

• Yes, frictional force is greater than centripetal foce

• No, frictional force is greater than centripetal force

• Yes, frictional force is less than centripetal force

• No, frictional force is less than centripetal force

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​Head to ppt. for slide 12

Open Ended

Any questions from today's lesson or parts that were confusing to you?