Physics 105, Fall Term, 2009
Reading: Chapters 7.1-7.3
Did you complete the reading assignment?
1) Rotational motion is really
the same as linear motion, with the same equations exchanging linear terms
with rotational terms.
2) The linear motion of an object at any
given point is the tangent to the point of the circle it is on.
A lot of people are intimidated by rotational motion; however, you only need to
use the same equations as with linear motion. The only change is exchanging
things like distance with angle, velocity with angular velocity, and
acceleration with centripetal acceleration. To see this conceptually, go to:
http://phet.colorado.edu/sims/rotation/rotation_en.jnlp and click on the
'Rotational' tab at the very top of the applet. There are boxes which you may
type in values for the variables you are looking at. You will also need to hit
the 'Clear' button below these boxes between each activity. Change the graph
options to showing the angle, angular velocity, and angular acceleration by
clicking the 'θ, ω, α' bubble.
With θ and α both at zero, change the angular velocity to 30 degrees/second and
press the 'Go' button directly below where you changed the value. Which best
represents the relationship of the angular position of the ladybug compared to
Constant, but not 0
Which best represents the relationship of the angular velocity of the ladybug
compared to time?
Which best represents the relationship of the angular acceleration of the
ladybug compared to time?
Change the angular velocity to 5 degrees/second and the angular acceleration to
30 degrees/second2. Which best represents the relationship of the
angular position of the ladybug compared to time?
Now change the graph settings to show linear velocity by clicking the 'θ, ω, v'
bubble. Start with the ladybug close to the center of the rotating platform and
change the angular velocity to 90 degrees per second and press 'Go'. While the
platform is spinning move the lady bug out toward the edge of the platform. How does this affect
Increases angular velocity
Decreases angular velocity
Angular velocity remains the same
How does this affect linear velocity?
Increases linear velocity
Decreases linear velocity
Linear velocity remains the same
What is the direction of the velocity vector?
The direction of linear velocity is always tangent to the circle that the ladybug moves along.
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Was there anything that you didn't understand in the reading assignment?
What was confusing to you?