Hovercraft B/C

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photolithoautotroph
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Re: Hovercraft B/C

Postby photolithoautotroph » April 19th, 2018, 12:39 pm

UTF-8 U+6211 U+662F wrote:
Tesel wrote:Consider a pipe with radius r.

If an ideal fluid is flowing through the pipe, how would the flow rate change if the radius was increased to 2r?

If a non-ideal, viscous fluid is flowing through the pipe, how would the flow rate change if the radius was increased to 2r?

Answer
Both fluids would go through twice as slowly?


Answers?
I haven't done enough fluid dynamics to be sure, but I can guess: for an ideal fluid the flow rate would change to 4Q (Q=Av) and for a non-ideal, viscous fluid, the flow rate would change to 16Q (Poiseuille's Law)? Less sure about the second one but either could be wrong. At least I don't actually have to do this for real.
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Re: Hovercraft B/C

Postby Tesel » April 19th, 2018, 7:52 pm

photolithoautotroph wrote:
UTF-8 U+6211 U+662F wrote:
Tesel wrote:Consider a pipe with radius r.

If an ideal fluid is flowing through the pipe, how would the flow rate change if the radius was increased to 2r?

If a non-ideal, viscous fluid is flowing through the pipe, how would the flow rate change if the radius was increased to 2r?

Answer
Both fluids would go through twice as slowly?


Answers?
I haven't done enough fluid dynamics to be sure, but I can guess: for an ideal fluid the flow rate would change to 4Q (Q=Av) and for a non-ideal, viscous fluid, the flow rate would change to 16Q (Poiseuille's Law)? Less sure about the second one but either could be wrong. At least I don't actually have to do this for real.


I should have clarified the question a lot better.
But yes, you made the right assumptions, and that was the correct use of Poiseuille's Law. Correct!
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Re: Hovercraft B/C

Postby CMS AC » May 1st, 2018, 10:19 am

photolithoautotroph wrote:
UTF-8 U+6211 U+662F wrote:
Tesel wrote:Consider a pipe with radius r.

If an ideal fluid is flowing through the pipe, how would the flow rate change if the radius was increased to 2r?

If a non-ideal, viscous fluid is flowing through the pipe, how would the flow rate change if the radius was increased to 2r?

Answer
Both fluids would go through twice as slowly?


Answers?
I haven't done enough fluid dynamics to be sure, but I can guess: for an ideal fluid the flow rate would change to 4Q (Q=Av) and for a non-ideal, viscous fluid, the flow rate would change to 16Q (Poiseuille's Law)? Less sure about the second one but either could be wrong. At least I don't actually have to do this for real.


Next question, please.

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Re: Hovercraft B/C

Postby photolithoautotroph » May 3rd, 2018, 4:19 pm

If nobody posts a question in this long, you can.
Question
Derive a formula for the acceleration of the blocks in a real atwood machine with two masses of mass and and a pulley in the shape of a uniform disk of mass and radius . The string is massless. Ignore friction.
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Re: Hovercraft B/C

Postby IvanGe » May 3rd, 2018, 4:51 pm

photolithoautotroph wrote:If nobody posts a question in this long, you can.
Question
Derive a formula for the acceleration of the blocks in a real atwood machine with two masses of mass and and a pulley in the shape of a uniform disk of mass and radius . The string is massless. Ignore friction.


a = m1g - m2g / m1+ m2
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Re: Hovercraft B/C

Postby UTF-8 U+6211 U+662F » May 3rd, 2018, 4:57 pm

photolithoautotroph wrote:If nobody posts a question in this long, you can.
Question
Derive a formula for the acceleration of the blocks in a real atwood machine with two masses of mass and and a pulley in the shape of a uniform disk of mass and radius . The string is massless. Ignore friction.

Answer
The acceleration of m1 where positive is down is


EDIT: Whoops, didn't see other answer

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Re: Hovercraft B/C

Postby PW240.3 » May 7th, 2018, 2:35 pm

photolithoautotroph wrote:If nobody posts a question in this long, you can.
Question
Derive a formula for the acceleration of the blocks in a real atwood machine with two masses of mass and and a pulley in the shape of a uniform disk of mass and radius . The string is massless. Ignore friction.



Since you have to account for the pulley's moment of inertia, wouldn't the a be a=(m1-m2)g/(m1+m2+M/4)

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Re: Hovercraft B/C

Postby IvanGe » May 7th, 2018, 6:18 pm

I'm just going to ask a question because no one's verified the answer.

With what constant velocity can a 4.00 hp motor raise a mass of 125 kg?
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Re: Hovercraft B/C

Postby Adi1008 » May 7th, 2018, 10:31 pm

IvanGe wrote:I'm just going to ask a question because no one's verified the answer.

With what constant velocity can a 4.00 hp motor raise a mass of 125 kg?

Answer
2.43 meters per second
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Re: Hovercraft B/C

Postby IvanGe » May 8th, 2018, 5:36 am

Adi1008 wrote:
IvanGe wrote:I'm just going to ask a question because no one's verified the answer.

With what constant velocity can a 4.00 hp motor raise a mass of 125 kg?

Answer
2.43 meters per second



that's what i got, but the answer key said 2.76 m/s?

Anyways, your turn
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Re: Hovercraft B/C

Postby UTF-8 U+6211 U+662F » May 9th, 2018, 1:19 pm

Adi1008 wrote:
IvanGe wrote:I'm just going to ask a question because no one's verified the answer.

With what constant velocity can a 4.00 hp motor raise a mass of 125 kg?

Answer
2.43 meters per second

Can you explain this one

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Re: Hovercraft B/C

Postby Tesel » May 9th, 2018, 1:32 pm

UTF-8 U+6211 U+662F wrote:
Adi1008 wrote:
IvanGe wrote:I'm just going to ask a question because no one's verified the answer.

With what constant velocity can a 4.00 hp motor raise a mass of 125 kg?

Answer
2.43 meters per second

Can you explain this one


So the first thing to understand is that hp is a unit of power, just not an SI unit. 1 hp = 745.7 W.
From here, we can use this relationship P = Fv to solve the equation.


The reason this works is that power is really a unit of energy per time. Energy, meanwhile, is a unit of force over a distance. So, power is a unit of force over a distance per time; the distance per time corresponds to velocity.
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Re: Hovercraft B/C

Postby UTF-8 U+6211 U+662F » May 9th, 2018, 1:34 pm

Tesel wrote:
UTF-8 U+6211 U+662F wrote:
Adi1008 wrote:
Answer
2.43 meters per second

Can you explain this one


So the first thing to understand is that hp is a unit of power, just not an SI unit. 1 hp = 745.7 W.
From here, we can use this relationship P = Fv to solve the equation.


The reason this works is that power is really a unit of energy per time. Energy, meanwhile, is a unit of force over a distance. So, power is a unit of force over a distance per time; the distance per time corresponds to velocity.

Ah, I see. Thanks!

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Re: Hovercraft B/C

Postby Adi1008 » May 9th, 2018, 10:26 pm

IvanGe wrote:
Adi1008 wrote:
IvanGe wrote:I'm just going to ask a question because no one's verified the answer.

With what constant velocity can a 4.00 hp motor raise a mass of 125 kg?

Answer
2.43 meters per second



that's what i got, but the answer key said 2.76 m/s?

Anyways, your turn

Suppose I have a bowling ball with a diameter of 25 centimeters. What is the largest mass it can have such that it floats in corn syrup (specific gravity = 1.4)?
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Re: Hovercraft B/C

Postby UTF-8 U+6211 U+662F » May 10th, 2018, 12:37 pm

Adi1008 wrote:Suppose I have a bowling ball with a diameter of 25 centimeters. What is the largest mass it can have such that it floats in corn syrup (specific gravity = 1.4)?

Answer

Last edited by UTF-8 U+6211 U+662F on May 10th, 2018, 7:11 pm, edited 1 time in total.


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