Answer:
The magnitude of angular acceleration is
.
Explanation:
Given that,
Initial angular velocity, 
When it switched off, it comes o rest, 
Number of revolution, 
We need to find the magnitude of angular acceleration. It can be calculated using third equation of rotational kinematics as :
So, the magnitude of angular acceleration is
. Hence, this is the required solution.
Answer:
The impression of the image on the retina lasts for about 1/16th of a second after the removal of the object. If a burning stick of incense is revolved at a rate of more than sixteen revolutions per second, we see a circle of red light due to persistence of vision.
Explanation:
Here in the process we require
1. Heat to melt down all ice
2. Heat to raise the temperature of whole water to 100 degree C
3. Heat to boil off the water
now here for the first part
Heat required to melt the ice


now heat required to raise the temperature to 100 degree C



Now heat required to boil it off


now the total heat required will be



so it required 287200 calorie heat to boil it all water