Answer:
7.5cm/s
Step-by-step explanation:
If V = velocity of water and r = radius of the pipe.
V is inversely proportional to the square of r
V = k/r^2, k = Vr^2, where k is the constant of proportionality.
When V = 30vm/s, r = 2
k = 30 × 2^2 = 30 × 4 = 120
therefore,
V = 120/r^2
When r = 4cm, then
V = 120/4^2 = 120/(4×4)
= 7.5cm/s
Velocity of water = 7.5cm/s