Physics
A metal cube of edge 5 cm and density 9.0 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)
[Hint: Tension in thread = apparent weight of the cube in liquid]
Fluids Upthrust
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Answer
Given,
Edges of cube = 5 cm
∴ Volume = 5 x 5 x 5 = 125 cm3
Density of metal = 9.0 g cm-3
Density of liquid = 1.2 g cm-3
Mass of the cube = volume of the cube x density of the cube
= 125 x 9
= 1125 g
Upthrust on cube = volume of the cube x density of the liquid x g
= 125 x 1.2 x g
= 150 gf
Tension in thread = Apparent weight of the cube in liquid
= true weight – upthrust
= 1125 - 150
= 975 kgf
= 9.75 N [∵ g = 10 ms-2]
Hence, tension in thread = 9.75 N
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