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# Circular Motion - PowerPoint PPT Presentation

Circular Motion. Uniform Circular Motion. Speed is constant, VELOCITY is NOT. Direction of the velocity is ALWAYS changing. Period (T) = time to travel around circular path once. (C = 2 π r). We call this velocity, TANGENTIAL velocity as its direction is TANGENT to the circle.

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## PowerPoint Slideshow about ' Circular Motion' - sugar

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Presentation Transcript

### Circular Motion

Speed is constant, VELOCITY is NOT.

Direction of the velocity is

ALWAYS changing.

Period (T) = time to travel around circular path once. (C = 2πr).

We call this velocity, TANGENTIAL velocity as its direction is TANGENT to the circle.

θ

Dv

v

v

Centripetal means “center seeking” so that means that the acceleration points towards the CENTER of the circle.

v

v

q

So for an object traveling in a counter-clockwise path. The velocity would be drawn TANGENT to the circle and the acceleration would be drawn TOWARDS the CENTER.

To find the MAGNITUDES of each we have:

Recall that according to Newton’s Second Law, the acceleration is directly proportional to the Force. If this is true:

NOTE: The centripetal force is a NET FORCE. It could be represented by one or more forces. So NEVER draw it in an FBD.

The blade of a windshield wiper moves through an angle of 90 degrees in 0.28

seconds. The tip of the blade moves on the arc of a circle that has a radius of 0.76m. What is the magnitude of the centripetal acceleration of the tip of the blade?

What is the minimum coefficient of static friction necessary to allow a penny to rotate along a 33 1/3 rpm record (diameter= 0.300 m), when

the penny is placed at the outer edge of the record?

Top view

FN

Ff

mg

Side view

Consider a satellite travelling in a circular orbit around Earth. There is only one force acting on the satellite: gravity. Hence,

Fg

There is only one speed a satellite may have

if the satellite is to remain in an orbit

Fg

Venus rotates slowly about its axis, the period being 243 days. The mass of Venus is 4.87 x 1024 kg. Determine the radius for a synchronous satellite in orbit around Venus. (assume circular orbit)

1.54x109 m

Today, Mr. Souza will give some notes about banked curves and vertical circular motion.

You may

• Sit in the first several rows in order to join the discussion about the above two topics

OR

• Sit towards the back part of the room and begin work on tonight’s homework:

• C&J p.150 # 21, 24, 26, 35, 36, 37, 40, 42

FN

FN cos(θ)

θ

A car of mass, m, travels around a banked curve of radius r.

FN sin(θ)

θ

W=mg

FN

FN cos(θ)

θ

Design an exit ramp so that cars travelling at 13.4 ms-1 (30.0 mph) will not have to rely on friction to round the curve (r = 50.0 m) without skidding.

FN sin(θ)

W=mg

θ

Gratuitous Hart Attack

NT

mg

mg

mg

NL

NR

NB

What minimum speed must she have to not fall off at the top?

mg

What minimum speed must she have to not fall off at the top?

NT

mg

mg

T

The maximum tension that a 0.50 m string can tolerate is 14 N.

A 0.25-kg ball attached to this string is being whirled in a vertical circle.

What is the maximum speed the ball can have

(a) at the top of the circle, and

(b)at the bottom of the circle?

(a)

(b) At the bottom?

T

mg

• C&J p.150 # 21, 24, 26, 35, 36, 37, 40, 42

• Please watch these two video clips (they relate to problem #37).