Question

A table tennis ball has radius $(3/2) × 10^{−2}$m and mass $(22/7) × 10^{−3}$kg. It is slowly pushed down into a swimming pool to a depth of 𝑑 = 0.7 m below the water surface and then released from rest. It emerges from the water surface at speed 𝑣, without getting wet, and rises up to a height 𝐻. Which of the following option(s) is(are) correct?[Given: $\pi = 22/7, g = 10 m s ^{−2}$, density of water = $1 × 10^3 kg\ m^{−3}$ , viscosity of water = $1 × 10^{−3}$ Pa-s.]

• A. The work done in pushing the ball to the depth 𝑑 is 0.077 J
• B. If we neglect the viscous force in water, then the speed 𝑣 = 7 m/s.
• C. If we neglect the viscous force in water, then the height 𝐻 = 1.4 m.
• D. The ratio of the magnitudes of the net force excluding the viscous force to the maximum viscous force in water is 500/9.

Answer 1

Answer: (A), (B), (D)

The work done in pushing the ball to the depth 𝑑 is 0.077 J

Answer 2

The correct option is (A): The work done in pushing the ball to the depth 𝑑 is 0.077 J, (B): If we neglect the viscous force in water, then the speed 𝑣 = 7 m/s. and (D): The ratio of the magnitudes of the net force excluding the viscous force to the maximum viscous force in water is 500/9.