Question

As you found out in the previous part, Bernoulli's equation tells us that a fluid element that flows through a flow tube with decreasing cross section moves toward a region of lower pressure. Physically, the pressure drop experienced by the fluid element between points 1 and 2 acts on the fluid element as a net force that causes the fluid to __________.

Answer 1

Answer:

Increase in speed.

Explanation: Since mass must be conserved, if the cross section of the flow tube is not the same, that is varies, the flow speed must change to conserve mass.

This means that there is a non-zero net force acting on the fluid that causes the fluid to increase or decrease in speed depending on whether the fluid is flowing through a portion of the tube with a smaller or larger cross

Answer 2

Answer:

As you found out in the previous part, Bernoulli's equation tells us that a fluid element that flows through a flow tube with decreasing cross section moves toward a region of lower pressure. Physically, the pressure drop experienced by the fluid element between points 1 and 2 (as shown in the attached image) acts on the fluid element as a net force that causes the fluid to __________

It causes the fluid to increase in speed

Explanation:

Bernoulli's equation determines the pressure at different points in a pipe. The Bernoulli's equation can be represented below;

$P_{1}$ + ½ ρ $v_{1} ^{2}$  = $P_{2}$ + ½ρ $v_{2} ^{2}$

Where $P_{1}$ is the pressure at point 1;

ρ is the density of the fluid;

$P_{2}$ is the pressure at point 2;

$v_{1} and v_{2}$ are the velocities at points 1 and 2 respectively.

Since the flow rate of the fluid is uniform across the pipe the behavior of the speed of flow across the pipe can be determined using the equation of flow rate;

$Q = A_{1}v_{1} = A_{2}v_{2}$

where Q is the flow rate, A is the cross-sectional area and v is the velocity at both ends.

Since the flow rate Q is the same at both ends, an increase in the area results in the corresponding decrease in the velocity in order to balance the flow rate across the pipe.

The net force causes an increase in the speed of the fluid at point 2. this is because the area of the pipe reduced at point 2 and it causes an increase in speed to normalize with the flow rate of the fluid