Question

g If a snowball melts so that its surface area decreases at a rate of 8 cm 2/min, find the rate at which the diameter decreases when the diameter is 9 cm.

Answer 1

Explanation:

The snowball is spherical in nature

The total surface area of the ball = 4πr²

Or 4π(d/2)²

S = 4πd²/4

S = πd²

d is the diameter of the ball

The rate at which the area is decreasing is expressed as;

dS/dt = dS/dd • dd/dt

dd/dt is the rate at which the diameter is decreasing

dS/dd = 2πd

dS/dt = 2πd • dd/dt

dS/dt = 2π(9) • dd/dt

8 = 18π•dd/dt

dd/dt = 8/18π

dd/dt = 4/9(3.14)

dd/dt = 4/28.26

dd/dt = 0.1415cm/min

Hence the diameter is decreasing at the rate of 0.1415cm/min