1. Rotation Again…

2. Remember…. Rotation speed = # of turns Rotational Period = 1 turn time
(rotational speed is focused on turns)
Rotational Period = turn
(rotational period is focused on time)

3. Example 1:
The rotational period of the earth is 1/day or 1/24hr. What is the rotation period of the earth in seconds?

4. Rotational Period is Inversely related to Frequencyƒ
T is period in seconds
ƒ is frequency in hertz (Hz)

5. Example 2:
What is the frequency of Saturn if it rotates on its axis once every 10hr 45 min 45 sec?

6. Angular Speed
2 people on a merry go round have the same period of rotation and the same angular speed. Although their linear speeds are very different.
Angular speed = rotation angle
time

7. Another way to write that formula…
ω = Θ ω is angular speed in rad/s
t Θ is angular displacement in rads
Θ = s s arc length in meters
r r is radius in meters
Θ in rads

8. Example 3:
While riding on a carousel a child travels through a arc length of 11.5m. If the carousel has a diameter of 8.00 meters, what is the child’s angular displacement?

9. Example 4:
If it took the child in example seconds to be displaced, what is her angular speed in rads/s? In degrees/s
(HINT: #rads(180/π) = degrees)