Calculate the kinetic energy AFTER the collision.

Initial kinetic energy KE = 1/2 m1v12 + 1/2 m2v22 = joules. The following calculation expects you to enter a final velocity for mass m1 and then it calculates the final velocity of the other mass required to conserve momentum and calculates the kinetic energy either gained or lost to make possible such a collision.

Explanation:

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 =