Question

A block of body weighs 15 N in springbalance in air and its weight in water shows 12 N. If the density of water is 1 gm/cc, what is the specific gravity of
the block ?

(A) 0.8
(B) 0.25
(C) 54
(D) 5
​

Answer 1

Answer:

B) 0.25

Explanation:

Answer 2

Given:

✰ Weight of a block of body in spring balance in air, W₁ = 15 N

✰ Weight of a block of body in water, W₂ = 12 N

✰ Density of water = 1 gm/cc

To find:

✠ The specific gravity of the block.

Solution:

The density of water is taken as a standard with which the densities of the other substances are compared. Thus, the relative density is also called specific gravity of a substance.

Step-by-step explanation:

➛ Upthrust acting on a block of body in water = W₁ - W₂

➛ Upthrust acting on a block of body in water = 15 - 12

➛ Upthrust acting on a block of body in water = 3 N

Now, find out the volume of the block of body.

⇾V = 3/10

⇾V = 0.3 cm³

Now, find out the mass of block of body.

We know that the Weight of a block of body in spring balance in air, W₁ = 15 N

⇾M = 15/10

⇾M = 1.5 g

✭ Density = Mass/Volume ✭

Putting the values in the formula, we have:

➤ Density = M/V

➤ Density = 1.5/0.3

➤ Density = (15 × 10)/(3 × 10)

➤ Density = 15/3

➤ Density = 5 g/cc

∴ The density of block = 5 g/cc

Now,

✭ R.D = Density of substance/Density of water ✭

Putting the values in the formula, we have:

➤ R.D = 5/1

➤ R.D = 5

∴ The specific gravity of the block = 5

N.B: Relative density is a number without units.

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