MHT CET 2021 Physics Solved Paper

(b) Let initial radius be r1.
Surface area of 1000 small water drops =1000×4πr12
Volume of 1000 small drops =1000×‌

4

3

πr13
Let final radius be r2.
Since, initial volume = final volume
1000×‌

4

3

πr13‌‌=‌

4

3

πr23
⇒ 1000r13‌‌=r23⇒‌

r2

r1

=10
Let us assume surface tension remain constant, i.e. S.
Therefore, ‌

(‌ Surface energy ‌)‌final ‌

(‌ Surface energy) ‌‌initial ‌

‌‌=‌

S×4πr22

S×4πr12×1000

‌‌=(‌

r2

r1

)2×‌

1

1000

=‌

1

10