Assignment 7 Query

#$&*

course Phy 122

2/10 9 pm

007. `query 6

*********************************************

Question: query introset How do we find the change in pressure due to diameter change given the original velocity of the flow and pipe diameter and final diameter?

YYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYY

Your Solution:

A1 * v1 = A2 *v2, which means that (v1 / v2) = (A2 / A1) making them proportional.

Since we know that (A2 / A1) = (d2 / d1)^2

Since we know that, we can then say that v2 = (d2 / d1)^2 * v1

Now we can plug this into Bernouilli's equation to find the change in pressure.

0.5 p (v1)^2 + pgh1 + P1 = 0.5 p (v2)^2 + pgh2 + P2

Now we want P2 - P1 on one side of the equal sign.

P2 - P1 = 0.5 p (v1)^2 + pgh1 - 0.5 p (v2)^2 - pgh2

Not sure that I did that right, I am quite confused about pressure so far.

confidence rating #$&*:

^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

.............................................

Given Solution:

** The ratio of velocities is the inverse ratio of cross-sectional areas.

Cross-sectional area is proportional to square of diameter. So velocity is inversely proportional to cross-sectional area:

v2 / v1 = (A1 / A2) = (d1 / d2)^2 so

v2 = (d1/d2)^2 * v1.

Since h presumably remains constant we have

P1 + .5 rho v1^2 = P2 + .5 rho v2^2 so

(P2 - P1) = 0.5 *rho (v1^2 - v2^2) . **

Your Self-Critique:

I have no idea if I did this right. I must admit that I am quite confused so far in this second part of Phy 122.

Your Self-Critique Rating:3

@&

Your explanation was good.

*@

*********************************************

Question: query video experiment terminal velocity of sphere in fluid. What is the evidence from this experiment that the drag force increases with velocity?

YYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYY

Your Solution:

After so many weights were placed on it, the velocity wasn't effected as much as before, therefore there must have been much friction, therefore as the velocity increased, the drag force also increased.

confidence rating #$&*:

^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

.............................................

Given Solution:

** When weights were repetitively added the velocity of the sphere repetitively increased. As the velocities started to aproach 0.1254 m/sec the added weights had less and less effect on increasing the velocity. We conclude that as the velocity increased so did the drag force of the water. **

Your Self-Critique:OK

Your Self-Critique Rating:OK

*********************************************

Question: `q001. If you know the pressure drop of a moving liquid between two points in a narrowing round pipe, with both points at the same altitude, and you know the speed and pipe diameter in the section of pipe with the greater diameter, how could you determine the pipe diameter at the other point?

YYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYY

Your Solution:

You could use Bernoulli's equation. Since h is constant, pgh could be taken out and you would be left with:

0.5 p (v1)^2 + P1 = 0.5 p (v2)^2 + P2

Now we can solve for v2 since v2 / v1 is proportional to A1 / A2, which will ultimately give us our diameter.

v2 = sqrt([(0.5 p (v1)^2 + P1 - P2) / (0.5 p)])

Therefore since we would know the value of the v2 and v1 and d1, we could now solve for d2 using the proportion we used earlier.

A1 * v1 = A2 * v2

(v2 / v1) = (A1 / A2) = (d1 / d2)^2

Therefore we need to square both sides I guess, but now I am not sure where to go from there.

I am still not sure if I did this correclty. All of this is quite confusing and I am trying to grasp it the best I can.

confidence rating #$&*:

^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

------------------------------------------------

Self-Critique Rating:

@&

You appear from your response to be doing very well.

*@

"

Self-critique (if necessary):

------------------------------------------------

Self-critique rating:

"

Self-critique (if necessary):

------------------------------------------------

Self-critique rating:

#*&!

&#This looks good. See my notes. Let me know if you have any questions. &#