If an object is moving with constant momentum ‹ 8, −15, −7 › kg · m/s,

a. What is the rate of change of momentum?
dp/dt=
b. What is the net force acting on the object?
Fnet=

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 =