The dumb questions thread

[Angry Floof]

Google is not forthcoming. It keeps throwing medical information at me. I just would like an explanation for why low dose aspirin comes in such an odd number for the dosage. 81mg. 81. Why not 80 or some other tidy number as we've come to expect for dosages? Diphenhydramine 25 mg makes sense. Fish oil 1,000 mg makes sense. 81 mg, no. Someone pls xpln.

Marketing?

The manufacturers of the 81 mg aspirin can honestly advertise that their aspirin is more powerful than their competition that has 80 mg aspirins.

I doubt it. It's 81 mg across brands. It's an aspirin thing.

Google is not forthcoming. It keeps throwing medical information at me. I just would like an explanation for why low dose aspirin comes in such an odd number for the dosage. 81mg. 81. Why not 80 or some other tidy number as we've come to expect for dosages? Diphenhydramine 25 mg makes sense. Fish oil 1,000 mg makes sense. 81 mg, no. Someone pls xpln.

Aspirin is quite old. The original Aspirin tablet was 5 grains. The grain is a unit of measurement of mass, and in the troy weight, avoirdupois, and Apothecaries' system, equal to exactly 64.79891 milligrams.*

5 grains = just less than 325 mg. 325/4 = 81 (rounded) so 1/4 tablet is then 81 mg or 5/4 grains.

*https://en.wikipedia.org/wiki/Grain_(unit)

Ah. Ok. That kind of makes sense. Sort of like the width of tracks left on the moon by astronaut vehicles is determined by the width of Roman war horses' rear ends.

 

[DBT]

They were talking about the results of a study on low dose aspirin on the ABC health report. It seems that taking low dose aspirin as a preventative has no benefits for those who do not have heart conditions, stints, etc....so, otherwise healthy individuals not only get no benefit but are at greater risk of hemorrhages and other problems associated with aspirin use.

 

[steve_bank]

They were talking about the results of a study on low dose aspirin on the ABC health report. It seems that taking low dose aspirin as a preventative has no benefits for those who do not have heart conditions, stints, etc....so, otherwise healthy individuals not only get no benefit but are at greater risk of hemorrhages and other problems associated with aspirin use.

It functions as a blood thinner, it helps prevent strokes and heart attacks for those with clogged blood vessels.r. It is less toxic than other thinners. If you take a large amount it can cause internal bleeding.

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A helicopter is sitting on a large area weight scale. The helicopter starts up and hovers just above the scale. What does the scale register?

 

[barbos]

Is there a shape, if made into a mirror, would reflect all light right back to its source? I.e. angle of reflection would always be 0 degrees, no matter which way light is coming from?

Yes, they even put it on the Moon.

 

[Bomb#20]

A helicopter is sitting on a large area weight scale. The helicopter starts up and hovers just above the scale. What does the scale register?

Glucose concentration. It also makes any nearby voltmeters register humidity. Helicopters are magic.[/Tom Sawyer]

 

[steve_bank]

A helicopter is sitting on a large area weight scale. The helicopter starts up and hovers just above the scale. What does the scale register?

Glucose concentration. It also makes any nearby voltmeters register humidity. Helicopters are magic.[/Tom Sawyer]

Obviously. Do you want the answer or do you give up?

 

[Wiploc]

I'll guess that--complicating factors ignored--the scales registers the same weight as before the copter took off. If it registered more, the copter would be rising.

 

[barbos]

A helicopter is sitting on a large area weight scale. The helicopter starts up and hovers just above the scale. What does the scale register?

will depend on the construction of the scale, if it's flat impenetrable for air surface it would register the same weight as before. But the size of the scale must be very large, much larger then hovering altitude.

 

[Bomb#20]

A helicopter is sitting on a large area weight scale. The helicopter starts up and hovers just above the scale. What does the scale register?

Glucose concentration. It also makes any nearby voltmeters register humidity. Helicopters are magic.[/Tom Sawyer]

Obviously. Do you want the answer or do you give up?

That's an odd pair of options. Neither. I know the answer -- it's a scale, it registers weight -- but the answer I gave you was more fun. But since you meant "How much does the scale register?", I know that answer too. It registers a chaotically varying amount of weight due to the air turbulence induced by the rotors, with a strong component of the variation at the frequency of the rotor times the number of rotor blades, and another component at the resonant frequency of the scale; and the weight registered will average some amount less than the weight of the helicopter, how much less depending on the size of the scale. (And on its permeability -- thanks barbos, I wouldn't have thought of that one.) The helicopter is supported by overpressure on the ground, and since the overpressure falls off gradually with distance, some of it is bound to extend beyond the edge of the scale. Unless the scale was specifically designed for measuring overpressure and sealed like a piston, the pressurized air will flow around the edges into the scale itself and push upward on the scale's weight-bearing surface, so you need to subtract not just the integrated overpressure beyond the scale but also the overpressure at the edge of the scale times the area of the scale.

 

[steve_bank]

It won't be perfect. The scale when the helicopter is hovering will read the same as the helicopter sitting on the scale engine off.

The kinetic energy in the air forced down equals the gravitational energy of the helicopter at hover. Newton's 3rd Law, equal and opposite reaction of the air hitting the scale.

Saw it demonstrated on a video, think it was Myth busters using a radio-controlled helicopter..

 

[Loren Pechtel]

A helicopter is sitting on a large area weight scale. The helicopter starts up and hovers just above the scale. What does the scale register?

Slightly less.

1) The helicopter is burning fuel, it's getting lighter.

2) A bit of the downdraft air misses the scale.

3) The helicopter is producing heat. The air is warmer, thus less dense.

All of these effects are obviously quite small.

 

[Bomb#20]

The kinetic energy in the air forced down equals the gravitational energy of the helicopter at hover. Newton's 3rd Law, equal and opposite reaction of the air hitting the scale.

Newton's 3rd Law is about force, not energy. "The kinetic energy in the air forced down equals the gravitational energy of the helicopter at hover." is just nonsense. The gravitational energy of the helicopter at hover rises linearly with altitude; the kinetic energy in the air forced down is nearly independent of altitude.

 

[steve_bank]

The kinetic energy in the air forced down equals the gravitational energy of the helicopter at hover. Newton's 3rd Law, equal and opposite reaction of the air hitting the scale.

Newton's 3rd Law is about force, not energy. "The kinetic energy in the air forced down equals the gravitational energy of the helicopter at hover." is just nonsense. The gravitational energy of the helicopter at hover rises linearly with altitude; the kinetic energy in the air forced down is nearly independent of altitude.

You can work through the dimensional analysis at your leisure. Conservation of energy always applies. Momentum of air as it hits the scale causes an equal and opposite reaction in Newtons. The link on statistical mechanics and pressure in a tank of gas is posted on another thread showing the derivation. That force adds to gravitational force m*g on the scale.See the link s on Quantization If Energy And Time thread.

F = m a. The force on the helicopter is mg down.

Consider a simple spring scale. It is force in Newtons that compresses the spring.

 

[Bomb#20]

The kinetic energy in the air forced down equals the gravitational energy of the helicopter at hover. Newton's 3rd Law, equal and opposite reaction of the air hitting the scale.

Newton's 3rd Law is about force, not energy. "The kinetic energy in the air forced down equals the gravitational energy of the helicopter at hover." is just nonsense. The gravitational energy of the helicopter at hover rises linearly with altitude; the kinetic energy in the air forced down is nearly independent of altitude.

You can work through the dimensional analysis at your leisure.

Okay, let's discuss your dimensional analysis error. The gravitational energy of the helicopter at hover is steady state energy. The kinetic energy in the air forced down is continuously delivered to air as it arrives above the rotors, so the helicopter transmits a certain amount of kinetic energy to the air per second that it's hovering. When you claim "The kinetic energy in the air forced down equals the gravitational energy of the helicopter at hover.", how many seconds does it take for the helicopter to give the air an amount of energy equal to the helicopter's gravitational energy?

 

[steve_bank]

You can work through the dimensional analysis at your leisure.

Okay, let's discuss your dimensional analysis error. The gravitational energy of the helicopter at hover is steady state energy. The kinetic energy in the air forced down is continuously delivered to air as it arrives above the rotors, so the helicopter transmits a certain amount of kinetic energy to the air per second that it's hovering. When you claim "The kinetic energy in the air forced down equals the gravitational energy of the helicopter at hover.", how many seconds does it take for the helicopter to give the air an amount of energy equal to the helicopter's gravitational energy?

I went through this to no end on the other thread derving pressure in pascals in a gas tank.

Read the link on statistical mechanics used to derive pressure in N/m^2 in a tank of gas. It is straightforward. The downward motion of the air created by the rotor blades exerts a pressure in Newtons/m^2 on the scale. Press on a scale with your hand and you exert pressure in pascals.The scale displays equivalent mass proportion to force your hand imparts to the scale.

Conservation of energy says the kinetic energy imparted to the air by the blades must equal the the weight of the copter, m*g. For steady state hover thrust must equal weight of the copter.

 

[Jokodo]

You can work through the dimensional analysis at your leisure.

Okay, let's discuss your dimensional analysis error. The gravitational energy of the helicopter at hover is steady state energy. The kinetic energy in the air forced down is continuously delivered to air as it arrives above the rotors, so the helicopter transmits a certain amount of kinetic energy to the air per second that it's hovering. When you claim "The kinetic energy in the air forced down equals the gravitational energy of the helicopter at hover.", how many seconds does it take for the helicopter to give the air an amount of energy equal to the helicopter's gravitational energy?

I went through this to no end on the other thread derving pressure in pascals in a gas tank.

Read the link on statistical mechanics used to derive pressure in N/m^2 in a tank of gas. It is straightforward. The downward motion of the air created by the rotor blades exerts a pressure in Newtons/m^2 on the scale. Press on a scale with your hand and you exert pressure in pascals.The scale displays equivalent mass proportion to force your hand imparts to the scale.

Conservation of energy says the kinetic energy imparted to the air by the blades must equal the the weight of the copter, m*g. For steady state hover thrust must equal weight of the copter.

So what you're saying is, Newtons per square meter and Newtons per square meter per second are the same thing and can be used interchangeably. In other words, time doesn't exist.

 

[bilby]

I went through this to no end on the other thread derving pressure in pascals in a gas tank.

Read the link on statistical mechanics used to derive pressure in N/m^2 in a tank of gas. It is straightforward. The downward motion of the air created by the rotor blades exerts a pressure in Newtons/m^2 on the scale. Press on a scale with your hand and you exert pressure in pascals.The scale displays equivalent mass proportion to force your hand imparts to the scale.

Conservation of energy says the kinetic energy imparted to the air by the blades must equal the the weight of the copter, m*g. For steady state hover thrust must equal weight of the copter.

So what you're saying is, Newtons per square meter and Newtons per square meter per second are the same thing and can be used interchangeably. In other words, time doesn't exist.

[Content removed.]

 

[steve_bank]

I went through this to no end on the other thread derving pressure in pascals in a gas tank.

Read the link on statistical mechanics used to derive pressure in N/m^2 in a tank of gas. It is straightforward. The downward motion of the air created by the rotor blades exerts a pressure in Newtons/m^2 on the scale. Press on a scale with your hand and you exert pressure in pascals.The scale displays equivalent mass proportion to force your hand imparts to the scale.

Conservation of energy says the kinetic energy imparted to the air by the blades must equal the the weight of the copter, m*g. For steady state hover thrust must equal weight of the copter.

So what you're saying is, Newtons per square meter and Newtons per square meter per second are the same thing and can be used interchangeably. In other words, time doesn't exist.

For all your posts you have not learned a thing.

 

[steve_bank]

I stand corrected. A helicopter hovers by drawing on Baby's emrgy that according to QFT is just 'every where'.....which QFT does not say.

It appears his his views come from scifi, which is why he can't explain as of yet how QFT depicts this energy that is everywhere.

Jocodo trys to jump into advanced issue but does not appear to have any facility with basic mechanics and physic 101..ie Newtons Laws. Ditto with LOT and the requirement ofa bonded system...etc etc etc.

 

[steve_bank]

Draw a circle representing the copter. Draw an up arrow labeled +f, and a down arrow from the circle labeled -f. Force vectors acting on the copter This boys and girls is called a free body diagram in mechanics and is a very very useful tool when used by experienced adults.Now listen closely...when +f = -f the copter is hovering. Are you with me so fat? Good. Okay so far jokodo? Good boy.

Now, the down force is -mg, the mass of the helicopter times gravitational acceleration from Newton's Laws. The up force is thrust from the helicopter blades. Those things that go round and round and round.

Now boys and girls a question for your homework in basic mechanics. A copter has a weight which can be measured on a scale on the ground, When the copter is hovering on what part of the copter bears the total weight?

After we answer that question boys and girls we will move on to the next step in the analysis.