One model of tennis ball launcher has advertised that it is capable of imparting 15,000 J of kinetic energy to a 0.5 kg ball initially at rest. A student carefully measures the compression of the spring to
be 0.10 m. What is the elastic energy stored in the spring?

to treat tumors in the body

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 =