## Question

Water flows into a horizontal pipe whose one end is closed with a valve and the reading of a pressure gauge attached to the pipe is . This reading of the pressure gauge falls to when the valve is opened. Calculate the speed of water flowing into the pipe.

### Solution

20 m/s

According to Bernoulli’s theorem, we have

Here *v*_{1} = 0 (the valve is initially closed, and so the velocity of water is zero).

.

Here (for water)

= 400 m^{2}/s^{2}

or *v*_{2} = 20 m/s.

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