Question

A cylinder of mass $10$ gram weighs $7$ gram in water. If its area of cross-section is $0.75/cm$, its length

• A. $4cm$
• B. $13.33cm$
• C. $9.33cm$
• D. None

Answer 1

The correct option is A $4cm$

Reduction in weight of the object is submerged in water is always equal to the weight of the liquid displaced.

The cylinder is submerged in water, and density of water is always 1g/cc.

Mass o the cylinder in the air= 10g

Mass of cylinder in the water= 7 g

Reducion in the weight of cylinder =10-7=3g

​ ​ ​

Area of crosssection = 0.75 cm2

​

​The mass of displaced water= Density of water × Volume of cylinder submerged

as we have know mass of displaced water is equal to reduction in weight of the object is submerged in water, and volume of cylinder is area of cross section multiplied by length L in cm)

3 = 1g/cc x (0.75 xL)

3= 0.75L

L= 3/0.75

L= 4cm

therefore length of cylinder is 4cm.