PHYSICS.. ALL ABOUT SPECIFIC GRAVITY, MASS & WEIGHT DENSITY.. HELP PLEASE..?

Question

please solve the following completely.. show your solutions. first answers which are correct and complete would get the best answer..!!

1) a piece of metal wood with a volume of 100cubic cm weighs 210g in water. how much does it weigh in air?

2) a balance weighs measures a mass of 90kg for a person and an apparent mass of 3.7kg when submerged in water. find the density of the person.

3) a person who weighs 170lb is found to weigh 81lbs when sumberged in water. find the weight density in pounds per cubic foot.

Answer 1

1) Buoyant force on the wooden block = Weight of water displaced by it = volume of block * density of water * g = (100/1000000) * 1000 * 10 = 1 N

(volume of block = 100 cm^3 = 100 / 1000000 m^3)

Weight in water (apparent weight) = 210 g = 210/100 kg = 0.21 * 10 N = 2.1 N

Actual weight = Apparent weight + Buoyant force = 3.1 N = 0.31 kg wt = 310 g wt

2) Actual weight = 90 kg wt

Apparent weight = 3.7 kg wt

So Buoyant force = Actual weight - Apparent weight = 86.3 kg wt.

Buoyant force = Volume of man * density of water * g

Find the volume of man.

Density = Mass / volume = 90 / Volume

3) This is same as (2)

Hope this helps.

[e-mail]