a block of a material of volume 20cmand density 2.5cm is suspended frm a spring balance wit half of the vol of the block immersed in a water,what is the reading of a spring balance?

vol = 20 cm^3 ?????

Your typing is very confusing

then upward force = weight of water displaced (Archimedes)
= 10 cm^3 * 1 gram/cm3 * g = 10 grams * g = .010 kg * 9.81 = .098 Newtons upward buoyancy

but
weight = volume * density * g
= 20 * 2.5 * 9.81/1000 = 0.49 N

difference = spring force = 0.39 N

the solving is not correct

To find the reading of the spring balance, we need to understand the basic principles of buoyancy and the concept of apparent weight.

First, let's understand the given information:
1. The volume of the block is 20 cm³.
2. The density of the block is 2.5 g/cm³.
3. Half of the volume of the block is immersed in water.

Now let's break down the steps to get the answer:

Step 1: Find the mass of the block.
The formula to find the mass of an object is:
Mass = Volume x Density
Given that the volume of the block is 20 cm³ and the density is 2.5 g/cm³:
Mass of the block = 20 cm³ x 2.5 g/cm³ = 50 g.

Step 2: Find the volume of the immersed part of the block.
Since half of the block's volume is immersed in water, the volume of the immersed part would be:
Volume of immersed part = 20 cm³ / 2 = 10 cm³.

Step 3: Find the buoyant force acting on the immersed part.
The buoyant force is the upward force acting on an object submerged in a fluid. It is equal to the weight of the fluid displaced by the object.
The formula to calculate buoyant force is:
Buoyant force = Density of the fluid x Gravity x Volume of the immersed part
Given that the density of water is approximately 1 g/cm³, and the volume of the immersed part is 10 cm³:
Buoyant force = 1 g/cm³ x 10 cm³ = 10 g.

Step 4: Find the apparent weight of the block.
The apparent weight is the effective weight experienced by an object when submerged in a fluid. It is the difference between the object's weight and the buoyant force.
The formula to calculate the apparent weight is:
Apparent weight = Weight - Buoyant force
Given that the mass of the block is 50 g, and the buoyant force is 10 g:
Apparent weight = 50 g - 10 g = 40 g.

Step 5: Convert the apparent weight to the reading of the spring balance.
The reading of a spring balance corresponds to the net force acting on an object, which is proportional to its weight.
Therefore, the reading of the spring balance for the block would be 40 g.

In conclusion, the reading of the spring balance would be 40 g.