Question

A body weighs $40g$ in air. If its volume is $10cc$, in water it will weight:

• A. $30g$
• B. $40g$
• C. $50g$
• D. none of there

Answer 1

The correct option is A $30g$

Given the volume of the body is $V=10\text{cc}$

Weight of the body in air is $W=40\text{g wt}$

By Archimedes principle, the buoyant force on the body when immersed in water is $B=\rho gV=1\text{g/cc}\times g\times 10\text{cc}=10\text{g wt}$

Thus, weight in water is $W^{\prime }=W-B=40-10=30\text{g wt}$