Answer:
Explanation:
Given
mass of sphere 
diameter of sphere 
radius 

friction will provide resisting torque so
where 







(b)time taken to decrease its rotational speed by 



Answer:
Post indicator valve
Explanation:
Post Indicator Valves are commonly used to control the water flow of sprinkler systems used in public and private buildings, warehouses, and factories for fire suppression. PIVs control water flow from the public system into the building's fire suppression system.
Answer: radio waves, microwaves, infrared waves.
Explanation:
Electromagnetic spectrum increases in wavelength and decreases with frequency in the following order
Gamma ray, X ray, Ultraviolet rays, Visible light, Infrared rays, Radio waves.
Since 397nm is greater than the value of visible spectrum, this shows that radio waves, microwaves and infrared wave falls in the spectrums of the wavelength value.