A girl of mass 48kg is rescued from a building fire by leaping into a firefighters' net. The window from which she leapt was 12 metres above the net. She lands in the net so that she is brought to a stop in 0.45 seconds. During this interval, a) What is her change in momentum?
b) What is the impulse on the net due to girl?
c) What is the average force on the net due to girl?

in simple terms, the principle states that the buoyancy force on an object is equal to the weight of the fluid displaced by the object, or the density of the fluid multiplied by the submerged volume times the gravitational acceleration, g. this is also known as upthrust.

that would be because of both gravity and friction. so     c

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 =