According to the Bernoulli's equation,the pressure difference between the wide and narrow ends of the pipe is given by
Here, 
is the velocity of water through wide ends of cylindrical pipe and 
is the velocity of water through narrow ends of cylindrical pipe.
Given, 
Now from equation continuity,
.
Here, 
and 
are cross- sectional areas of wide and narrow ends of cylindrical pipe.
As pipe is circular, so
.
At the second point, the diameter is halved, which means the radius is also halved. Therefore,
Substituting these values with the density of water is 
in pressure difference formula we get.
To calculate the momentum, you have to use the equation p=mv or p to mass times velocity.
Answer: A.
As a diver rises, the pressure on their body decreases which allows the volume of the gas to decrease.
Explanation:
The problem is that a diver, experiences an increased pressure of water compresses nitrogen and more of it dissolves into the body. Just as there is a natural nitrogen saturation point at the surface, there are saturation points under water. Those depend on the depth, the type of body tissue involved, and also how long a diver is exposed to the extra pressure. The deeper a diver go, the more nitrogen the body absorbs.
The problem is getting rid of the nitrogen once you ascend again. As the pressure diminishes, nitrogen starts dissolving out of the tissues of the diver's body, a process called "off-gassing." That results in tiny nitrogen bubbles that then get carried to the lungs and breathed out. However, if there is too much nitrogen and/or it is released too quickly, small bubbles can combine to form larger bubbles, and those can do damage to the body, anything from minor discomforts all the way to major problems and even death.
