Question

A body of volume 100 cm3 weighs 1 kgf in air. Find (i) it’s weight in water and (ii) it’s relative density

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Answer

Volume of body = 100 cm3

Weight of the body in air (W1) = 1 kgf = 1000 gf

Let the weight of the body in water be W2

Density = Mass\over Volume

= 1000\over 100 = 10 g cm-3

RD of body = 10\over 1 = 10

Now, RD of the body = W_1\over W_1 - W_2

⇒ 10 = 1000\over 1000 - W_2

⇒ 10 (1000 – W2) = 1000

⇒ 1000 – W2 = 100

⇒ W2 = 1000 – 100 = 900 gf

Hence,

(i) Weight in water = 900 gf

(ii) Relative density of body = 10

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