Question

the weight of a stone water is 55 newton and weight in air 80 Newton find buoyancy​

Answer 1

Weight difference =

150-100 = 50 N = Buoyant force of water

Buoyant Force in water(Fb) = density of water x g x volume of body(Vb)

50 = 1000 x 9.81 x Vb

Vb = 50/9810 cubic meter

Now, in air

Weight of body = mg = 150 N

Mass of body,m = 150/9.81 Kg

So,

Density of body = m/ Vb

= 150/9.81 ÷ 50/9810

= 3000 kg per cubic meter

Specific gravity of body = density of body ÷ density of water

= 3000 ÷ 1000

Specific gravity of body = 3.

Answer 2

As we know that

By Archimedes' Principle

When a body is immersed in a fluid , partially or wholly , it experiences an upward force equal to the weight of the volume of the fluid displaced by it.

So when a body is weighed in water its weight is lossed due to upward force (Buoyant Force).

So,

Loss in weight = buoyant force on the immersed body

Weight (in air) - weight (in liquid) = buoyant force —(equation-1)

Weight (in air) = weight (in liquid) + buoyant force

buoyant force = 80 N - 55 N

buoyant force = 25 N