Hovercraft B/C

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Re: Hovercraft B/C

Postby UTF-8 U+6211 U+662F » March 15th, 2018, 2:39 pm

Justin72835 wrote:
UTF-8 U+6211 U+662F wrote:
Justin72835 wrote:Do you need to know anything about initial and final velocities to solve this question?

Whoops: They are moving toward each other, the ball with a speed of 5 m/s and the pencil with a speed of 0.4 m/s.

Answer
Alright, first find the final velocities of both of the objects.





Plugging in the given values and solving for the final velocities gives 4.946 m/s for the ball and 10.346 m/s for the pencil. Now you can find the average force on the pencil:



This gives an average force of 0.0107 N. You can check this answer by doing the same calculation on the ball (Newton's Third Law).

Yep, your turn! Wolfram alpha link to the series of equations if anyone wants it: Link

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Re: Hovercraft B/C

Postby Justin72835 » March 15th, 2018, 2:51 pm

UTF-8 U+6211 U+662F wrote:Yep, your turn! Wolfram alpha link to the series of equations if anyone wants it: Link


Awesome :D

An amusement park is planning on constructing a new ride and needs help with all the planning. The track begins at a height of 60 meters and slopes downward at a constant angle. The coefficient of rolling friction for the wheels of the roller coaster is 0.05. If the park wants the ride to have a final velocity of at least 25 m/s at its lowest point, what should the minimum angle of slope be?
Last edited by Justin72835 on March 15th, 2018, 4:55 pm, edited 1 time in total.
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Re: Hovercraft B/C

Postby UTF-8 U+6211 U+662F » March 15th, 2018, 4:11 pm

Justin72835 wrote:An amusement park is planning on constructing a new ride and needs help with all the planning. The track begins at a height of 60 meters and slopes downward at a constant angle. The coefficient of rolling friction for the wheels of the roller coaster is 0.05. If the park wants the ride to have a final velocity of at least 25 m/s at its lowest point, what should the minimum angle of slope be?

Answer

















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Re: Hovercraft B/C

Postby Justin72835 » March 15th, 2018, 4:57 pm

UTF-8 U+6211 U+662F wrote:
Justin72835 wrote:An amusement park is planning on constructing a new ride and needs help with all the planning. The track begins at a height of 60 meters and slopes downward at a constant angle. The coefficient of rolling friction for the wheels of the roller coaster is 0.05. If the park wants the ride to have a final velocity of at least 25 m/s at its lowest point, what should the minimum angle of slope be?

Answer

















Correct! You're next!
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Re: Hovercraft B/C

Postby UTF-8 U+6211 U+662F » March 15th, 2018, 5:24 pm

A 1 kg hovercraft is plugged into a power source with a 14 m long wire. It floats 2 cm off the ground and goes around in a circle around the power source at 6 m/s. The fans the hovercraft uses "convert" 1 Joule of energy into 1 Newton of force every second. Find the wattage of the power source.

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Re: Hovercraft B/C

Postby Justin72835 » March 16th, 2018, 12:06 am

UTF-8 U+6211 U+662F wrote:A 1 kg hovercraft is plugged into a power source with a 14 m long wire. It floats 2 cm off the ground and goes around in a circle around the power source at 6 m/s. The fans the hovercraft uses "convert" 1 Joule of energy into 1 Newton of force every second. Find the wattage of the power source.

Answer
First find the power needed to keep the the hovercraft floating:



Next, find the centripetal force acting on the hovercraft:





Adding the two gives an answer of 2.78 W.
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Re: Hovercraft B/C

Postby UTF-8 U+6211 U+662F » March 16th, 2018, 5:31 pm

Justin72835 wrote:
UTF-8 U+6211 U+662F wrote:A 1 kg hovercraft is plugged into a power source with a 14 m long wire. It floats 2 cm off the ground and goes around in a circle around the power source at 6 m/s. The fans the hovercraft uses "convert" 1 Joule of energy into 1 Newton of force every second. Find the wattage of the power source.

Answer
First find the power needed to keep the the hovercraft floating:



Next, find the centripetal force acting on the hovercraft:





Adding the two gives an answer of 2.78 W.

Not quite
Does the lift fan really use more energy when the hovercraft is higher? Use a free-body diagram.

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Re: Hovercraft B/C

Postby Justin72835 » March 18th, 2018, 4:44 am

UTF-8 U+6211 U+662F wrote:
Not quite
Does the lift fan really use more energy when the hovercraft is higher? Use a free-body diagram.

Take 2.0


Next, find the centripetal force acting on the hovercraft:





Adding the two gives an answer of 12.37 W.

Hope this is right :oops:
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But in ourselves, that we are underlings."


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Re: Hovercraft B/C

Postby UTF-8 U+6211 U+662F » March 18th, 2018, 8:18 am

Justin72835 wrote:
UTF-8 U+6211 U+662F wrote:
Not quite
Does the lift fan really use more energy when the hovercraft is higher? Use a free-body diagram.

Take 2.0


Next, find the centripetal force acting on the hovercraft:





Adding the two gives an answer of 12.37 W.

Hope this is right :oops:

Almost
Do the hovercraft fans power the centripetal force or does the tension in the wire?

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Re: Hovercraft B/C

Postby Justin72835 » March 18th, 2018, 8:56 am

UTF-8 U+6211 U+662F wrote:
Justin72835 wrote:
UTF-8 U+6211 U+662F wrote:
Not quite
Does the lift fan really use more energy when the hovercraft is higher? Use a free-body diagram.

Take 2.0


Next, find the centripetal force acting on the hovercraft:





Adding the two gives an answer of 12.37 W.

Hope this is right :oops:

Almost
Do the hovercraft fans power the centripetal force or does the tension in the wire?

Final effort
Is it just 9.8 W?
"The fault, dear Brutus, is not in our stars,
But in ourselves, that we are underlings."


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Re: Hovercraft B/C

Postby UTF-8 U+6211 U+662F » March 18th, 2018, 8:58 am

Justin72835 wrote:
UTF-8 U+6211 U+662F wrote:
Justin72835 wrote:
Take 2.0


Next, find the centripetal force acting on the hovercraft:





Adding the two gives an answer of 12.37 W.

Hope this is right :oops:

Almost
Do the hovercraft fans power the centripetal force or does the tension in the wire?

Final effort
Is it just 9.8 W?

Yep :lol: Of course, it would be more if I remembered to specify a coefficient of friction

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Re: Hovercraft B/C

Postby Justin72835 » March 18th, 2018, 6:52 pm

UTF-8 U+6211 U+662F wrote:Yep :lol: Of course, it would be more if I remembered to specify a coefficient of friction

A uniform 0.4 m long stick rotates freely about a horizontal axis through one of its ends. It is released at an unknown angle to the vertical. When it hangs straight down, the speed of the tip of the stick is 3.5 m/s. How large is the unknown angle?
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Re: Hovercraft B/C

Postby UTF-8 U+6211 U+662F » March 20th, 2018, 7:28 pm

Justin72835 wrote:A uniform 0.4 m long stick rotates freely about a horizontal axis through one of its ends. It is released at an unknown angle to the vertical. When it hangs straight down, the speed of the tip of the stick is 3.5 m/s. How large is the unknown angle?

Kind of confused here. Might be asking too much, but could you draw a picture?

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Re: Hovercraft B/C

Postby Adi1008 » March 20th, 2018, 8:24 pm

UTF-8 U+6211 U+662F wrote:
Justin72835 wrote:A uniform 0.4 m long stick rotates freely about a horizontal axis through one of its ends. It is released at an unknown angle to the vertical. When it hangs straight down, the speed of the tip of the stick is 3.5 m/s. How large is the unknown angle?

Kind of confused here. Might be asking too much, but could you draw a picture?

I think this picture shows what he's talking about:

Image

The rod rotates in the plane of the page
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Re: Hovercraft B/C

Postby UTF-8 U+6211 U+662F » March 20th, 2018, 9:18 pm

Ohh, I see.
Answer


Not really sure since I still haven't quite wrapped my head around rotational stuff.

EDIT: Over-complicated things the first attempt


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