Question

A jet of water 75 mm in diameter having velocity of 20 m/s strikes 9 series of flat plates arranged around the periphery of a wheel such that each plate appears successively before the jet. if the plates are moving at a velocity of 5 m/s , compute the force exerted by the jet on the plate , the work done per second on the plates and efficiency of the jet

Answer 1

The work done on the jet plates is 4972.5 N.m

Explanation:

Given data:

• Diameter of jet = 75 mm
• velocity of water = 20 m/s
• Velocity of plates = 5  m/s

Solution:

Area of jet:

a = π / 4 (75 / 1000)^2

a = 0.0442 m^2

The normal thrust on a moving flat plate on the plate  

F = w a ( v − u)^2 g

F = 9810 × (0.00442)(20 − 5)^2 / 9.81 = 994.5 N

Work done per second by the jet on the plate

= F×u

= (994.5 × 5) = 4972.5 N.m

Hence the work done on the jet plates is 4972.5 N.m