Answer:
Explanation:
Given:
- diameter of the CD,
- initial rotational speed of the CD,
- rotational acceleration of CD,
- maximum speed of rotation after acceleration,
- time of constant angular velocity,
- time taken to stop the rotation after the acceleration is stopped,
- time of observation from the start,
<u>Now the time taken to get to the maximum angular velocity:</u>
using equation of motion,
<u>Now we observe the time to be in the deceleration phase, by:</u>
- So the phase after 25 seconds from the start is the phase of deceleration of the disk by 5 seconds.
<u>Now the angular acceleration during the phase:</u>
using eq. of motion,
where:
final angular velocity of the disk during the phase
acceleration during the deceleration phase
<u>Now the speed at the instant of 5 seconds of the deceleration phase:</u>
<u>The angular distance travelled by the disk during this 5 seconds:</u>
....................................(1)
<u>Now the angular distance travelled in the phase of acceleration:</u>
.....................................(2)
Now the angular acceleration during the constant angular speed phase:
........................(3)
Now the total angular distance travelled by any point on the disk will be same:
so, from (1), (2) and (3)