(b) Internal diameter for hose pipe, d1=4cm,r1=‌
d
2
=‌
4
2
=2cm=2×10−2m Speed of water through hose pipe, v1=1ms−1 Speed of water through nozzle, v2=4ms−1 Diameter, d2= ? According to principle of continuity, ‌A1v1=A2v2 ⇒‌πr12v1=πr22v2 ⇒‌r22=‌
r12v1
v2
⇒r22=‌
(2×10−2)2×1
4
⇒‌r22=10−4 ⇒‌r2=10−2m⇒r2=1cm ∴‌‌ Diameter of nozzle, ‌d2=2r2=2×1=2cm