# PHYSICS HELP:What is the distance from the top of the block to the water if the water is fresh?

PHYSICS HELP: What is the distance from the top of the block to the water if the water is fresh?

A 10cm by 10 cm by 10 cm wood block with a density of 700kg/{m}^{3} floats in water.

a.What is the distance from the top of the block to the water if the water is fresh?

b.If it's seawater?

by

(a).

density of fresh water is ρ_water = 1000 kg/m³

ΣF = 0

- (ρ_wood)g(V_wood) + (ρ_water)g(v_wood) = 0

(v_wood)/(V_wood) = (ρ_wood)/(ρ_water)

(10 * 10 * h)/(10 * 10 * 10) = (700)/(1000)

h = 7 cm

the distance from the top of the block to the water is 10 - 7 = 3 cm

(b).

density of seawater is ρ_sea = 1030 kg/m³

(v_wood)/(V_wood) = (ρ_wood)/(ρ_sea)

(10 * 10 * h')/(10 * 10 * 10) = (700)/(1030)

h' = 6.79611 cm

the distance from the top of the block to the water is 10 - 6.79611 = 3.20389 cm

Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat.
by

if an object floats in water then the fraction of its volume that floats inside water is fiven by

d1/d1 ...where d1=density of the floating object and d2=density of water

hence fraction of volume of wood that floats inside water is given by

700/1000 (density of water=100 kg/m^3)

=0.7 part of volume floats inside water

hence 0.3 part of of vulme floats outside water

now volume of wood=10 *10*10=1000 cm^3 =10^-3 cubic metre

hence volume of wood outside water=0.3 *10^-3= 3*10^-4 cubic metre

height of block from water * base area =volume outside water

h*10 ^-2 metre sq.=3*10^-4 metre cube

h=3* 10^-2 m= 3 cm...this is the answer

Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat.
by

The wood is 70% of the weight of the water, so 70% of the wood will submerge leaving 30% floating above water line.

a. distance above water = 3 cm

--------------------------------------------

b. Seawater weighs 1030 kg /m^3

700 / 1030 = 67.96 % as heavy as seawater

100% - 67.96% = 32.04 % of wood will be above waterline

.3204* 10cm = 3.2 cm of wood will be above waterline

Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat.