The dumb questions thread

[barbos]

I agree wholeheartedly.

OK... Now I am trying to work out how that could possibly be engineered.

I did not tell you you to do that. I told you imagine it's already there.

Are you sure that this isn't getting even more over complicated?

then everything (including air) above it will be registered. The fact that something does not have direct contact with the scale is irrelevant. The only effect is due to the altitude because weight of the object depends on the distance to the earth but it's rather small because radius of the earth is so much larger than helicopter altitude (1/r^2 factor)

Yeah, I am pretty sure that this isn't making things less complicated.

It does, it allows to get rid of all aerodynamics

Let's try this - Imagine a helicopter hovering. As it isn't moving vertically, we can confidently assert that the lift is exactly equal to the weight.

and?

 

[Wiploc]

Imagine whole earth surface being a scale,

OK... Now I am trying to work out how that could possibly be engineered. Are you sure that this isn't getting even more over complicated?

It helps to remember that you're on Diskworld.

 

[Wiploc]

Great. Now all we need to know is the planet, air pressure, and altitude where equivalence is achieved to determine gravity force. Or am I missing something.

You're missing the little button that zeros the scale before the helicopter takes off.

 

[steve_bank]

Great. Now all we need to know is the planet, air pressure, and altitude where equivalence is achieved to determine gravity force. Or am I missing something.

You're missing the little button that zeros the scale before the helicopter takes off.

Experience counts....

 

[steve_bank]

You fasten two pieces of metal together with a nut and bolt. What makes the nut and bolt work?

 

[James Brown]

As a junior engineer interviewing at Intel the manager asked me a question.

In 0g a sealed sphere is filled with oxygen. A very small candle is somehow lit at the center of ball. Will the candle stay lit as long as the O2 is not used up?

I've seen an experiment on this done in space. The flame emits CO2 which, because it's in 0g, doesn't rise away but instead forms a perfect sphere around the flame, eventually snuffing out the candle.

 

[Loren Pechtel]

As a junior engineer interviewing at Intel the manager asked me a question.

In 0g a sealed sphere is filled with oxygen. A very small candle is somehow lit at the center of ball. Will the candle stay lit as long as the O2 is not used up?

We already know the answer--it goes out.

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You fasten two pieces of metal together with a nut and bolt. What makes the nut and bolt work?

The nut and bolt are just sitting there. Work?!?!

(The real answer is friction.)

 

[steve_bank]

As a junior engineer interviewing at Intel the manager asked me a question.

In 0g a sealed sphere is filled with oxygen. A very small candle is somehow lit at the center of ball. Will the candle stay lit as long as the O2 is not used up?

We already know the answer--it goes out.

- - - Updated - - -

You fasten two pieces of metal together with a nut and bolt. What makes the nut and bolt work?

The nut and bolt are just sitting there. Work?!?!

(The real answer is friction.)

Tightening the nut stretches the bolt which acts like a spring. That is force that creates the friction against the nut's threads.

- - - Updated - - -

As a junior engineer interviewing at Intel the manager asked me a question.

In 0g a sealed sphere is filled with oxygen. A very small candle is somehow lit at the center of ball. Will the candle stay lit as long as the O2 is not used up?

I've seen an experiment on this done in space. The flame emits CO2 which, because it's in 0g, doesn't rise away but instead forms a perfect sphere around the flame, eventually snuffing out the candle.

I did not look it up but I figured there was an experiment. My answer was a general no because without gravity there is no convection currents. I did not think of combustion products.

 

[Bomb#20]

There fore at any point in time during hover the average total kinetic energy in the moving air partcles must equal mg of the helicopter.

What are the units for the average total kinetic energy in the moving air particles?

What are the units for mg of the helicopter?

 

[steve_bank]

There fore at any point in time during hover the average total kinetic energy in the moving air partcles must equal mg of the helicopter.

What are the units for the average total kinetic energy in the moving air particles?

What are the units for mg of the helicopter?

Energy, work and heat are Joules.

f = ma os Newton's 2nd Law applied to gravity.

Force in Newton = mass in kilograms x acceleration.

F = m*a = m*g where g is gravitational acceleration. When you step on a scale there is a force don on the scale in Newtons equal to your body mass in kilograms times g.

Newtons = kg * 9.8m/s^2.

Force in Newtons is an SI definition.
https://en.wikipedia.org/wiki/Newton's_laws_of_motion\\You can googl gravity and newton's laws for examples.

 

[bilby]

There fore at any point in time during hover the average total kinetic energy in the moving air partcles must equal mg of the helicopter.

What are the units for the average total kinetic energy in the moving air particles?

Energy is measured in Joules, or kg.m².s^-2

What are the units for mg of the helicopter?

m is mass in kg; g is the acceleration due to gravity in m.s^-2, so mg is measured in Newtons, or kg.m.s^-2

The claim "the average total kinetic energy in the moving air partcles must equal mg of the helicopter" cannot be correct, as it can be reduced to the claim that n Joules equals m Newtons, which is an impossibility.

Once again, Steve has failed basic dimensional analysis; and once again he has offered a placeholder for an answer, rather than answering a very simple question with a very simple answer - presumably either because he realized his error and didn't want to admit it, or because he is so arrogant that he refuses to check his work at all.

 

[fromderinside]

You're missing the little button that zeros the scale before the helicopter takes off.

Not really. I'm from the A/C industry and I know standards are avoided like the plague. Costs money, got a waiver., these things never go out of calibration, etc. So I presumed the mechanism underlying the function of the button hadn't been recertified in the last three, six, twelve, 24 months.

Always best to go to original measurements. Does the above take care of your experience thingie steve_bank?

 

[steve_bank]

You're missing the little button that zeros the scale before the helicopter takes off.

Not really. I'm from the A/C industry and I know standards are avoided like the plague. Costs money, got a waiver., these things never go out of calibration, etc. So I presumed the mechanism underlying the function of the button hadn't been recertified in the last three, six, twelve, 24 months.

Always best to go to original measurements. Does the above take care of your experience thingie steve_bank?

I will always defer to the wisdom of an old grey beard...

 

[Loren Pechtel]

We already know the answer--it goes out.

- - - Updated - - -



The nut and bolt are just sitting there. Work?!?!

(The real answer is friction.)

Tightening the nut stretches the bolt which acts like a spring. That is force that creates the friction against the nut's threads.

Yeah, but without the friction that tension does nothing. Still, however, a physicist will say there's no work being done.

As a junior engineer interviewing at Intel the manager asked me a question.

In 0g a sealed sphere is filled with oxygen. A very small candle is somehow lit at the center of ball. Will the candle stay lit as long as the O2 is not used up?

I've seen an experiment on this done in space. The flame emits CO2 which, because it's in 0g, doesn't rise away but instead forms a perfect sphere around the flame, eventually snuffing out the candle.

I did not look it up but I figured there was an experiment. My answer was a general no because without gravity there is no convection currents. I did not think of combustion products.

CO2 buildup, O2 depletion, same effect--the fire goes out. Note that it's very nasty--up there every candle (and most other burnable things) is a relighting candle. Convection doesn't remove the heat, if the air moves (which can be simply someone passing by!) and you've got fire again.

 

[steve_bank]

It is textbook, Applying the specified torque for a fastener stretches the bolt but not beyond its elastic limit. WI thought the spring force of the bolt there is not enough friction.

Work is done applying torque.

In the candle problem without gravity there is no convention currents. There is conduction. In gravity light hot gas rises and heavy cool gas falls.

Air and liquid water are both fluids in fluid mechanics.

Put a cube of ice in the middle of a tank of water and what happens. Water cooled next to a face on the ice cube drops crating a vertical current drawing warm water to the face.

.

 

[steve_bank]

Imagine a rigid triangle frame with a .7 meter side a 1.5 meter side, and a 1 meter base. The triangle is sat up on the 1 meter side and a 100kg weight is placed on the peak.

On each piece what is the force in Newtons acting along each piece.

On the the base piece what is the force in Newtons at the joints on each end pulling the base peace apart.

The helicopter problem, was a problem in dynamics. This is a problem in statics.

If that is too easy, add a piece connecting the mid[pints of the two triangle sides and calculate the forces acting in line with each piece.

 

[steve_bank]

It is easier to see it the problem as a mass on an inclined plane. A Little trig to calculate the normal force component and the force parallel to the inclined plane.

A good summary of forces, see the free body diagram of a mass on an inclined plane down on the right.


https://en.wikipedia.org/wiki/Force#Gravitational

Adding friction to the problem
http://www.understandingforce.com/calculatingfriction.html

https://www.physicsclassroom.com/class/vectors/Lesson-3/Resolution-of-Forces

For a triangle supporting say a pipe drop a line from the peak normal to the base to divide into two right triangles.. Then calculate how the force = mg divided between the two legs . Static forces are linear, the total tension or stretching force on the base leg is the sum of the x components from the two triangles..


Or

https://www.easycalculation.com/trigonometry/learn-triangle-law-of-forces.php

 

[steve_bank]

In baseball why does a left handed pitcher have an advantage over a right handed batter?

 

[steve_bank]

In baseball why does a left handed pitcher have an advantage over a right handed batter?

For the sports unsophisticated.

Breaking pitches result from spil on the ball and position of stitches when the ball is thrown. Due to the natural motion of the arm and wrist a breaking balk thrown by a lefy handed pitcher breaks in a way that is more difficukt for a right handed batter to see and hit.

A hitter with better eyesight can see the spin as it leaves the pitcher and judge what the pitch is.

http://www.exploratorium.edu/baseball/activities/thrown-for-a-curve.html
https://lokeshdhakar.com/baseball-pitches-illustrated/
http://ffden-2.phys.uaf.edu/211_fall2002.web.dir/jon_drobnis/curveball.htm

Baseballs, a sconce based sport. The bat has a resonant sweet spot. If the ball os hit on the sweet spot max energy is imparted to the ball. When the spot is hit cleanly on the spot it has a unique sound. Modern hitting coaching is based on physics. Developing swings based on angles of swing, a particular pitch, and where you want then ball to go.

Right and left hand hitters have a tendency to hit to one side of the field. Some pitchers are good at inducing ground balls or fly balls.

 

[steve_bank]

The ends of a string are attached to a wall with a tension. On one end a pulse deflection is induced in the positive vertical direction.

The disturbance which looks like a rounded pulse propagates towards the other end. As it reaches the other end and the string tries to rise against the fixed point on the wall what happens on the string?