Need Help With Masses of Objects?

Question

One cubic centimeter (1.0 cm3) of water has a mass of 1.0 10-3 kg.

(a) Determine the mass of 1.0 m3 of water.

_______kg

(b) Assuming biological substances are 98% water, estimate the masses of

a cell with a diameter of 1.0 µm,

_________kg

a human kidney, and

_________kg

a fly.

_________kg

Assume a kidney is roughly a sphere with a radius of 4.0 cm, and a fly is roughly a cylinder 4.0 mm long and 2.0 mm in diameter.

Note: Density is defined as the mass of an object divided by its volume .

Answer 1

♠proportion:

1cm^3 ~ 1e-3 kg;

1m^3 ~ m, hence m=1e-3*1e6/1 = 1000 kg = 1 ton;

♠ assuming 2% is void we get:

m = volume *density *percentage;

m = [(4/3)*pi *(0.5e-6)^3 m^3] *[1000 kg/m^3] *0.98 =5.13e-16 kg;

m = [(4/3)*pi *(4e-2)^3 m^3] *[1000 kg/m^3] *0.98 =0.2627 kg;

m = [pi*(1e-3)^2 *4e-3 m^3] *[1000 kg/m^3] *0.98 =1.2315e-5 kg;

note: v of sphere = (4/3)*pi *r^3, v of cyl = pi*r^2*h;