A metal cube of edge 5 CM and density is 9 g/cm³is suspended by a thread so as to be completely immersed in a liquid 1.2 g/cm³. Find upthrust and density.
Answers
Volume of metal cube = (5 cm)3 = 125 x 10−6 m3.
Density of metal = 9 g/cm3 = 9000 kg/m3.
Mass of the metal cube m = volume x density
= 125 x 10−6 m3.9000 kg/m3.
= 1.125 kg
Weight of the metal cube in air = mg = 1.125 kg x 10 m/s2 = 11.25 N
Volume of liquid displaced = Volume of metal cube = 125 x 10−6 m3.
Mass of liquid displaced = Volume x density of liquid
= 125 x 10−6 m3.1200 kg/m3.
= 0.15 kg
Weight of liquid displaced = 0.15 kg x 10 m/s2 = 1.5 N = upthrust
Weight of metal cube in liquid = Weight of the metal cube in air - upthrust
= 11.25 − 1.5
= 9.75 N
Therefore tension in the string = 9.75 N.
Similarly you can calculate the quantities in the next problem.
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