The radius of a circular soap bubble is increasing at the rate of 0.2

1.	The radius of a circular soap bubble is increasing at the rate of 0.2 cm/s. Find the rate of increase of its surface area when the radius is 7 cm.
Answer» We know that a soap bubble will be in sphere shape Consider the radius of soap bubble as r dr/dt = 0.2 cm/s The surface area of soap bubble = 4 πr² So the rate of change of surface area = 8πr dr/dt By substituting the values = 8 × 3.14 × 7 × 0.2 We get dS/dt = 35.2 cm²/s

The radius of a circular soap bubble is increasing at the rate of 0.2 cm/s. Find the rate of increase of its surface area when the radius is 7 cm.

Answer»

We know that a soap bubble will be in sphere shape

Consider the radius of soap bubble as r

dr/dt = 0.2 cm/s

The surface area of soap bubble = 4 πr²

So the rate of change of surface area = 8πr dr/dt

By substituting the values

= 8 × 3.14 × 7 × 0.2

We get

dS/dt = 35.2 cm²/s