Sally places a jar with some pennies into a pool of water and exactly half of the jar is submerged. The volume of the jar is 200 cm3 and the density of the water is 1 g/cm3.

a. What is the buoyant force acting on the jar?
b. What is the weight of the jar and pennies?
c. What is the density of the combined jar and pennies?

Bouyant Force = 0.9N

The density of the jar and Penny was not given so we can't determine it's weigh and combined density

Explanation:

Bouyant force Fb = Volume of solid*density of liquid*acceleration

Fb= (200/2)*1*980.665

Fb= 98066.5/100000

Fb= 0.9N

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 =