A metal cube of edge 5 cm and density 9 g cm-3 is suspended by a thread so as to be completely immersed in a liquid of density 1.2 g cm-3. Find the tension in thread. (Take g = 10 m s-2)

Question

A metal cube of edge 5 cm and density 9 g cm^-3 is suspended by a thread so as to be completely immersed in a liquid of density 1.2 g cm^-3. Find the tension in thread. (Take g = 10 m s^-2)

Sum

Solution

Given, side of the cube = 5 cm

∴ volume of the cube = 5 × 5 × 5 = 125 cm³

Density of metal = 9.0 g cm^-3

Density of liquid = 1.2 g cm^-3

Mass of the cube = volume × density

= 125 × 9 = 1125 g

∴ weight of the cube = 1125 gf (downwards)

Upthrust on cube = weight of the liquid displaced

= volume of the cube × density of liquid × g

= 125 × 1.2 ×

= 150 gf (upwards)

Tension in thread = Net downward force

= Weight of cube - Upthrust on cube

= 1125 − 150

= 975 kgf

= 9.75 N ...[∵ g = 10 m s^-2]

Hence, tension in thread = 9.75 N

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Determination of Relative Density of a Solid Substance by Archimedes’ Principle

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Q 8 Q 7 Q 9

Chapter 5: Upthrust in Fluids, Archimedes’ Principle and Floatation - Exercise 5 (A) [Page 111]

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Selina Concise Physics [English] Class 9 ICSE

Chapter 5 Upthrust in Fluids, Archimedes’ Principle and Floatation
Exercise 5 (A) | Q 8 | Page 111

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