One end of a piano wire is wrapped around a cylindrical tuning peg and the other end is fixed in place. the tuning peg is turned so as to stretch the wire. the piano wire is made from steel (y = 2.0x1011 n/m2). it has a radius of 0.55 mm and an unstrained length of 0.75 m. the radius of the tuning peg is 1.0 mm. initially, there is no tension in the wire, but when the tuning peg is turned, tension develops. find the tension in the wire when the tuning peg is turned through two revolutions.

Explanation:

When the screw is turned by two turns then change in the length of the wire is given as

now we know by the formula of Young's modulus

so we have

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 =