From the concept of optics on a curvature of a spherical mirror, the proportion for which the focal length is equivalent to half the radius of curvature is fulfilled. Mathematically this is

Here,
f = Focal Length
R = Radius
Rearranging to find the radius we have,

Replacing with our values,
R = 2(13.8cm)
R = 27.6cm
Therefore the radius of the spherical surface from which the mirror was made is 27.6cm
Answer:
The angular velocity of the propeller is 2.22 rad/s.
Explanation:
The angular velocity (ω) of the propeller is:
Where:
θ: is the angular displacement = 10.6 revolutions
t: is the time = 30 s

Therefore, the angular velocity of the propeller is 2.22 rad/s.
I hope it helps you!
Answer:
Cell Membrane
Explanation:
The cell membrane controls what goes in and out of a cell, and keeps it shape, much like a city limit.
Answer:
Insulation helps to prevent that transfer of heat.