Question

Two small balls of same size and masses m₁ and m₂ (m₁> m₂) are tied by a thin weightless thread and dropped from a certain height. Taking upward buoyancy force F into account the tension T of the thread during the flight after the motion of the balls becomes uniform will be-

• A. (m₁ – m₂)g
• B. (m₁ – m₂) $\frac{g}{2}$
• C. (m₁ + m₂)g
• D. (m₁ + m₂) $\frac{g}{2}$

Answer 1

Answer: (B)

(m₁ – m₂) $\frac{g}{2}$

Answer 2

F_b = Buoyancy force of air

m₁ : m₁g = T + F_b …….(1)

m₂ : m₂g + T = F_b ……. (2)

From eq. (1) & (2)

m₁g – T = m₂ g + T

T = $\frac{(m_{1}–m_{2})g}{2}$