Question

How do I find the gravitation force, or weight, of a 1-inch thick cylindrical steel tank that's submerged underwater given the weight density of steel to be 500 lb/ft^3? The radius is 5 ft and the length is 15 ft.

Answer 1

since thickness of the steel cylinder = 1 inch =1/12 = 0.083

so, R₀ = outer radius = 5 +0.083 = 5.083 feet and R_i = inner radius = 5 feet

Volume of the steel cylinder = .(R₀² -R_i²).h

= .( 5.083² - 5²).15

= 39.6 ft³

and since density = mass / volume

so , mass = density * volume

= 500 x 39.6

= 19798.58 lbs ( as 1 pound = 0.445 kg then 19798.58 x 0.445 = 8810.37 kg)

= 8810.37 kg

so gravitation force, or weight, = m.g

= 8810.37 x 9.8

= 86341.61 N