Hovercraft B/C

Test your knowledge of various Science Olympiad events.
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Re: Hovercraft B/C

Postby UTF-8 U+6211 U+662F » February 13th, 2018, 1:47 pm

Riptide wrote:
UTF-8 U+6211 U+662F wrote:What is an integrated hovercraft?

Wasn't too sure on what this could be but it looks like it is a hovercraft in which "only one propeller is used to provide both lift and thrust air". These questions however are no longer a part of hovercraft (fortunately) so no point to really learn these facts or add them to your binder (although questions like these have showed up in an invitational for me earlier this year).

Oh whoops, I could've sworn the test section didn't change. Oh well, that's right. Your turn!

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Re: Hovercraft B/C

Postby Riptide » February 13th, 2018, 4:30 pm

A circle rotates clockwise at 100 rpm and has a constant counterclockwise acceleration of 4 rad/s^2 for 5.5 seconds. What is the angular displacement?
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Re: Hovercraft B/C

Postby Justin72835 » February 13th, 2018, 5:53 pm

Riptide wrote:A circle rotates clockwise at 100 rpm and has a constant counterclockwise acceleration of 4 rad/s^2 for 5.5 seconds. What is the angular displacement?

Answer
100 rpm = 10.47 rad/s (multiply by pi/30). Then using rotational kinematics (use the displacement equation), you get an answer of 2.9 rad counterclockwise.
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Re: Hovercraft B/C

Postby Riptide » February 14th, 2018, 9:54 am

Justin72835 wrote:
Riptide wrote:A circle rotates clockwise at 100 rpm and has a constant counterclockwise acceleration of 4 rad/s^2 for 5.5 seconds. What is the angular displacement?

Answer
100 rpm = 10.47 rad/s (multiply by pi/30). Then using rotational kinematics (use the displacement equation), you get an answer of 2.9 rad counterclockwise.

Nicely done! Your turn
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2018: Game On/Helicopters/Forensics/Hovercraft/Fermi Questions

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Re: Hovercraft B/C

Postby mattruff » February 14th, 2018, 12:19 pm

Are we allowed do put Lego wheels on the sides of our hovercraft to help the hovercraft roll against the sides ?

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Re: Hovercraft B/C

Postby Riptide » February 14th, 2018, 12:34 pm

mattruff wrote:Are we allowed do put Lego wheels on the sides of our hovercraft to help the hovercraft roll against the sides ?

Sounds like an interesting idea :?: . Not too sure if it’d be allowed but try asking on the actual hover forum I’m sure some discussion will spur on it.
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Re: Hovercraft B/C

Postby Justin72835 » February 14th, 2018, 2:53 pm

Riptide wrote:
Justin72835 wrote:
Riptide wrote:A circle rotates clockwise at 100 rpm and has a constant counterclockwise acceleration of 4 rad/s^2 for 5.5 seconds. What is the angular displacement?

Answer
100 rpm = 10.47 rad/s (multiply by pi/30). Then using rotational kinematics (use the displacement equation), you get an answer of 2.9 rad counterclockwise.

Nicely done! Your turn

A hammer with mass m is dropped from rest from a height h above the earth's surface. This height is not necessarily small compared with the radius Re of the earth. If you ignore air resistance, derive an expression for the speed v of the hammer when it reaches the surface of the earth. Your expression should involve h, Re, and me, the mass of the earth.
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Re: Hovercraft B/C

Postby Adi1008 » February 14th, 2018, 6:26 pm

Justin72835 wrote:
Riptide wrote:
Justin72835 wrote:
Answer
100 rpm = 10.47 rad/s (multiply by pi/30). Then using rotational kinematics (use the displacement equation), you get an answer of 2.9 rad counterclockwise.

Nicely done! Your turn

A hammer with mass m is dropped from rest from a height h above the earth's surface. This height is not necessarily small compared with the radius Re of the earth. If you ignore air resistance, derive an expression for the speed v of the hammer when it reaches the surface of the earth. Your expression should involve h, Re, and me, the mass of the earth.

Answer
When the hammer moves towards the Earth, its gravitational potential energy becomes a bigger negative number. This results in the "release" of some kinetic energy in the form of the hammer moving by the Conservation of Energy.
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Re: Hovercraft B/C

Postby Justin72835 » February 14th, 2018, 7:03 pm

Adi1008 wrote:
Answer
When the hammer moves towards the Earth, its gravitational potential energy becomes a bigger negative number. This results in the "release" of some kinetic energy in the form of the hammer moving by the Conservation of Energy.

Good job; I guess it's your turn now!
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Re: Hovercraft B/C

Postby Adi1008 » February 14th, 2018, 7:19 pm

Justin72835 wrote:
Adi1008 wrote:
Answer
When the hammer moves towards the Earth, its gravitational potential energy becomes a bigger negative number. This results in the "release" of some kinetic energy in the form of the hammer moving by the Conservation of Energy.

Good job; I guess it's your turn now!

A uniform stick of length is fixed at one end and is free to rotate in the plane of the computer screen. It is initially released at an angle to the vertical. When the stick has fallen to the point where it hangs straight down, the speed at the tip is . What is ?
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Re: Hovercraft B/C

Postby Riptide » February 14th, 2018, 7:43 pm

Adi1008 wrote:A uniform stick of length is fixed at one end and is free to rotate in the plane of the computer screen. It is initially released at an angle to the vertical. When the stick has fallen to the point where it hangs straight down, the speed at the tip is . What is ?

Answer
Drawing a diagram makes it easier to answer this question. The initial height is (L/2)*(1+cos ). Using conservation of energy we get 3L(1+cos ) = v^2, which results in = arccos(v^2/(3Lg)-1).
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Re: Hovercraft B/C

Postby Adi1008 » February 14th, 2018, 7:47 pm

Riptide wrote:
Adi1008 wrote:A uniform stick of length is fixed at one end and is free to rotate in the plane of the computer screen. It is initially released at an angle to the vertical. When the stick has fallen to the point where it hangs straight down, the speed at the tip is . What is ?

Answer
Drawing a diagram makes it easier to answer this question. The initial height is (L/2)*(1+cos ). Using conservation of energy we get 3L(1+cos ) = v^2, which results in = arccos(v^2/(3Lg)-1).

Looks good bro. Your turn!
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Re: Hovercraft B/C

Postby Riptide » February 14th, 2018, 7:54 pm

A 8 gram bullet is fired horizontally with a speed of 400 m/s into a 1.2 kg block of wood at rest on the floor. If the coefficient of friction between the block and the table is 0.2, A) how far will the block slide and B) what fraction of the bullet's energy is dissipated in the collision itself?
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Re: Hovercraft B/C

Postby Justin72835 » February 15th, 2018, 1:38 pm

Riptide wrote:A 8 gram bullet is fired horizontally with a speed of 400 m/s into a 1.2 kg block of wood at rest on the floor. If the coefficient of friction between the block and the table is 0.2, A) how far will the block slide and B) what fraction of the bullet's energy is dissipated in the collision itself?

Answer
,
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Thermodynamics: 3/-

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Re: Hovercraft B/C

Postby Riptide » February 15th, 2018, 1:40 pm

Justin72835 wrote:
Riptide wrote:A 8 gram bullet is fired horizontally with a speed of 400 m/s into a 1.2 kg block of wood at rest on the floor. If the coefficient of friction between the block and the table is 0.2, A) how far will the block slide and B) what fraction of the bullet's energy is dissipated in the collision itself?

Answer
,

Nice work your turn!
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