Faina says that an object cannot be in mechanical equilibrium when only a single force acts on it. do you agree or disagree? explain.

A single force can't bring mechanical equilibrium. As the third law of Newton which very fresh and deliberately worded: To each action, there is dependably an equivalent and inverse response. The third law implies by action, the force. So the forces exist in pairs. Besides, by equilibrium, we mean either the body is rest or in uniform movement (both transnational or rotational) because of no external force or net external force is zero by the first law of motion. Thus no mechanical equilibrium condition is acquired by one single force.

Hence, I agree with Faina statement.

total distance/total time

(85 + 82)/(5+3)

167/8

20 just over

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 =