3 The given sketch shows a common consumer product called th

3. The given sketch shows a common consumer product called the Water Pik. This device uses the motor to drive a piston pump that produces a jet of water (d = 1mm, T = 10C) with a speed of 27 m/s. Estimate the minimum electrical power in watts that is required by the device. Hints: (a) Assumed that the power is used only to produce the kinetic energy of the water in the jet and (b) in a time interval At, the amount of mass that flows out the nozzle is m, and the corresponding amount of kinetic energy is (2/2). (10 points) Highiged Meotor and Fig: Abstracted from Elger, Lebret, Crowe, & Roberson 11th Edition Fluid Mechanics. 2016 John Wiley and Sons. 4. Water flows at a steady rate in this vertical pipe. The pressure at A is 10 kPa, and at B it is 98.1 kPa. The flow in the pipe is (a) upward, (b) downward, or (c) no flow. (Hint: see problem 6) (10 points)

Solution

Problem 4.

Answer is B downward sincle fluid always flows from low pressure to high pressure.

Problem 3.

The density of water at 10 c is 999.025 kg/m3

Minimum power required = m v2 / 2

E = p A v * v2/2

p = density

A = area = / 4 ( 1/1000)^2 = 7.853x10^-7 m2

So therefore

E =( 999.025 *7.853x10^-7*27^3)/2

E =7.72 Watts