Question
If 1000 droplets of water of surface tension 0.07 N / m . having same radius 1 ~mm each, combine to from a single drop. In the process the released surface energy is( Take . = 22 7 )
BITSAT
Physics
Mechanical Properties of Fluids
2023
BITSAT 2023 (Memory Based Paper 1)
BITSAT Physics Question (2023) — Solution
Options
- A. 7.92 10^ -6 ~J
- B. 7.92 10^ -4 ~J
- C. 9.68 10^ -4 ~J
- D. 8.8 10^ -5 ~J
Answer
B. 7.92 10^ -4 ~J
Step-by-step solution
We have V_f=V_i 4 3 r_ f ^3=1000 4 3 r _ i ^3 r _ f ^3=1000 r _ i ^3 r_f=10 r_i So, released energy = Initial surface energy - final surface energy =1000 T 4 r _ i ^2- T 4 r _ f ^2 =4 T (1000 r _ i ^2- r _ f ^2 ) =4 0.07 (1000 r _ i ^2-100 r _ i ^2 ) =4 0.07 900 r_i^2 =4 63 10^ -6 =7.92 10^ -4 ~J
Related: Physics — Mechanical Properties of Fluids · All PYQ Banks