Answer:
1.) 15,708cm^2/s
2) 47,124cm^2/s
3.) 109,956cm^2/s
Step-by-step explanation:
Given the following:
50cm/s is the radius of the ripple per second , that is, radius(r) of ripple after t seconds = speed * time(t)
Speed = 50cm/s
r = 50t
.area of a circle(A) = πr^2
Rate of change of area with radius :
dA/dt = π2r . dr/dt
Speed of ripple created = 50cm/s; this is the rate at which the radius changes with time (dr/dt)
dr/dt = 50cm/s
Rate at which area is increasing with time:
dA/dt = π2r . dr/dt
dA/dt = π2(50t).50
dA/dt = 5000πt
After 1 second:
dA/dt = 5000π(1)
= 15,707.963cm^2/s
After 3 second:
dA/dt = 5000π(3)
= 47,123.889cm^2/s
After 7 second:
dA/dt = 5000π(7)
= 109,955.74cm^2/s
