Question
Question: On dropping a stone in stationary water circular ripples are observed. Rate of flow of ripples is 6 ...
On dropping a stone in stationary water circular ripples are observed. Rate of flow of ripples is 6 cm/sec. when radius of the circle is 10cm, then fluid rate of increase in its area is :
A
120 cm2/sec
B
p cm2/sec
C
120p cm2/sec
D
None
Answer
120p cm2/sec
Explanation
Solution
dtdr = 6cm/sec
A = pr2
dtdA= 2pr .dtdr = 2p × 10 × 6
= 120p cm2/sec