Title: Force%20and%20Motion-II:%20continued%20Friction%20and%20Drag;Circular%20Motion
1Force and Motion-II continuedFriction and
DragCircular Motion
- Lecture 6
- Monday2 February 2004
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9UNIFORM CIRCULAR MOTION
10CIRCULAR MOTION
- When an object travels in a circle, its velocity
is constantly changing (in direction-at least). - That means the object has a non-zero acceleration
even if it moves at constant speed.
11What is the direction of this acceleration?
12Acceleration in Circular Motion
- Centripetal acceleration
- Direction
- Toward the center of the circle
- Magnitude
13FORCES IN CIRCULAR MOTION
- An unbalanced force must cause the acceleration.
14Using Freebody Diagrams to Analyze Forces
Twirl a ball attached to a string in a vertical
circle. What forces act on the ball and what are
the direction of these forces?
15Using Freebody Diagrams to Analyze Forces
What forces act on the ball and what are the
direction of these forces?
Top
a
T
Are we missing a force? (the centripetal force)?
Is the acceleration g?
W
T
Bottom
a
W
16Using Freebody Diagrams to Analyze Forces
What forces act on the ball and what are the
direction of these forces?
Top
a
-T-Wm(-a) or TWma
T
W
T-Wma
T
Bottom
a
Are we missing a force? (the centripetal force)?
Is the acceleration g?
W
17Any force can be a centripetal force.
-Gravitational Attraction -Tension in a
string -Normal Force -A push or pull
Does the planet in orbit here have a
gravitational force AND a centripetal force
acting on it?
18PERIOD IN CIRCULAR MOTION
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