A table tennis ball has an average density of 0.084 g/cm^3 and a diameter of 3.8 cm. What force can submerge the ball in water? (density of water is 1 gm/cm^3)a) 1.0 N b) 0.79 N c) 0.52 N d) 0.26

1 Answer

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justaguide | College Teacher | (Level 2) Distinguished Educator

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The density of the table tennis ball is 0.084 g/cm^3. This has to be converted in terms of SI units. It is equal to 0.084*10^-3/(0.01)^3 kg/m^3 = 84 kg/m^3. The density of water is 1 g/cm^3 which is equal to 1000 kg/m^3. The diameter of the tennis ball is 3.8 cm or 0.038 m.

When a ball is submerged in water, the force or resistance is equal to the weight of the volume of water displaced from which the weight of the ball is subtracted.

Here, the force of resistance is (1000 - 84)*9.8*(4/3)*pi*(0.038/2)^3

=> 0.26 N

To submerge the ball, a force equal to the force of resistance has to be applied, which is equal to 0.26 N

The correct answer is option d. 0.26 N