Q2 A source of frequency 500 Hz emits waves of wavelength 0.2m. How long does it take the waves to
travel 400m?

4 secs

Explanation:

The first step is to calculate the velocity

V= frequency × wavelength

= 500× 0.2

= 100

Therefore the time can be calculated as follows

= distance/velocity

= 400/100

= 4 secs

The power input is 0.102 kW

Solution:

As per the question:

Length of the loop, L = 40 m

Diameter of the loop, d = 1.2 cm

Velocity, v = 2 m/s

Loss coefficient of the threaded bends,

Loss coefficient of the valve,

Dynamic viscosity of water,

Density of water,

Roughness of the pipe of cast iron,

Efficiency of the pump,

Now,

We calculate the volume flow rate as:

where

= Volume rate flow

A = Area

v = velocity

For this, Reynold's N. is given by:

Since, > 4000, the flow is turbulent in nature.

Now,

With the help of the Colebrook eqn, we calculate the friction factor as:

f = 0.05075

Now,

To calculate the total head loss:

Now,

The drop in the pressure can be calculated as:

Now,

to calculate the input power: