A 2 kg ball rolls off a 26 m high cliff, and lands 29 m from the base of the cliff. Express the displacement and the gravitational force in terms of vectors and calculate the work done by the gravitational force. Note that the gravitational force is < 0, -mg, 0 >, where g is a positive number (+9.8 N/kg). (Let the origin be at the base of the cliff, with the +x direction towards where the ball lands, and the +y direction taken to be upwards.)

Explanation:

mass of ball, m = 2 kg

height along negative Y axis, h = 26 m

distance along positive X axis, d = 29 m

Displacement in vector form is

Gravitational force, mg downwards

Work done by the gravitational force

W = 2 x 9.8 x 26 = 509.6 Joule

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 =