You are designing a rotating metal flywheel that will be used to store energy. The flywheel is to be a uniform disk with a radius of 23.0 cm. Starting from rest at t = 0, the flywheel rotates with constant angular acceleration 3.00 rad/s^2 about an axis perpendicular to the flywheel at its center.
If the flywheel has a density (mass per unit volume) of 8600 kg/m^3, what thickness must it have to store 800 J of kinetic energy at t = 8.00 s?

Explanation:

Given that

Radius of disk is

r=23cm=0.23m

The disk starts from rest at t=0

Given angular acceleration

α=3rad/s²

Density of disk is p=8600kg/m³

Energy stored K.E=800J

time taken t=8s

Thickness?

Check attachment for solution

it is given that trillions of microbes make up to 1% to 3% of the body mass.

let's take average of this percentage: 2%

consider the average mass of the human body as 70 kg.

then, trillions of microbes would have mass  

therefore, 100 trillion micro-organisms would weigh:

this is an approximate value and could change depending on the mass of the human body and percentage of the microbes present in it.

average mass per microorganism =