Brain busters

[Midwest]

Need more info, I normally follow accoustic guitars as Im learning one but can't recall unless you narrow it down for us.

Twas this guy; http://www.electriciansforums.co.uk/threads/funny-youtube-videos.16576/

post 11 by Paul M.

 

[Darkwood]

Question 3 - Answer.

It looks like we have a winner (post 50 ElectroChem).

All you need to do is create a T with the 2 pieces of metal, if the vertical piece is the magnet it will stick to the middle of the horizontal steel and vice versa if the vertical is the steel it won't stick to the horizontal piece because it is at the centre of the bar magnet where there is no real magnetic effect, the ends of the magnet contain the strong fields N and S.

 

[Darkwood]

Question 4 - Heating things up.

I decided to go to bed and set the heating to stay on for 1hr before it clicks off, assuming the heating stays on constantly and warms the room then can I take it that the air within the room now has more energy in it when the hour is up and the room is warmer?... No simple yes/no answers, please explain your answer.

 

[Kamikaze]

Energy can be stored or transferred in different ways from place to place and this includes gasses. Hot gasses contain more energy than cold gasses. At an atomic level, the kinetic energy of the atoms increase with temperature which means more electrons have the energy needed to move a current. Although the increased temperature will also have increased the resistance of the gasses. Which now makes me think that the increased stored energy in the air can not be used unless it is changed back into something else. I feel I’ve forgotten something important but I cant remember what it is?

 

[Wilko]

Energy is put into the room by the heater and this is seen by the temp rising, somewhere. The air in the room is warmed by the heater and by contact with the walls of the room which are heated by radiation, and in fact by DW himself if he stays in room. But the air may be "changed out" by ventilation and so if there is sufficient draught (and the outside air temp is low etc) then room air temp may be lower.
Assuming powerful radiator and correct insulation and ventilation, then air temp rises and hotter air has more energy. Where's my brandy?

 

[Darkwood]

Not seeing anyone near yet, the actual answer is one of three:-

The air within the room contains -

-MORE
-LESS
-THE SAME AMOUNT OF

energy after the heating has warmed the room up.

Note the room temperature has risen over this hour period, this is not a trick question either, all answers must have an explanation.

 

[Wilko]

Ok - more - heat input makes the air molecules move faster which is seen as temp increase. Just like my hot cup o tea

 

[Kamikaze]

Energy is put into the room by the heater and this is seen by the temp rising, somewhere. The air in the room is warmed by the heater and by contact with the walls of the room which are heated by radiation, and in fact by DW himself if he stays in room. But the air may be "changed out" by ventilation and so if there is sufficient draught (and the outside air temp is low etc) then room air temp may be lower.
Assuming powerful radiator and correct insulation and ventilation, then air temp rises and hotter air has more energy. Where's my brandy?

That’s it! You’ve hit the nail on the head there. The heat losses in the room through conduction needs to heat the outside world to at least the same temperature before the temperature can begin to rise inside the room. The very reason heaven is hotter than hell. The good thing is, we can now blame global warning on DW for leaving the heating on and going to bed. Give it another 50 years and we will be able to go swimming in the see without a hat and scarf on.

 

[Darkwood]

You lads are not getting the jist of this thread, I post brainteasers that you may think you know the answer to but when you think about it, it more complex, no one has touched on the correct answer or the reason.
I can say that the air temp does in deed rise but losses to walls furniture etc are not a concern and from this post you should work out the the total energy level of the air must now either remain the same or be less considering I just said no one has given the correct answer yet.

Back over to you

 

[Kamikaze]

I’ve cheated and asked my mate Margot Gerritsen for the answer and she send me this...lol.

View attachment 35521

 

[Darkwood]

Close kamikaze but she made a big blunders the third line

 

[Des 56]

Time to waffle some more nonsense from this feeble brain of mine

The air is warmed,the warm air has greater volume,air now needs to vacate the premises or the premises needs to get bigger
The volume of the warmed air is more energetic than previous, but, because there is less of it, the total energy remains the same

 

[Kamikaze]

Close kamikaze but she made a big blunders the third line

She’s a good teacher but she’s no Einstein.

Non-random arrangements of energies are not valued in calculations. Also, since the still air velocity is also zero. Any calculation would involve multiplying, dividing or square rooting by zero. So any answer to that equation would be = 0.

 

[Darkwood]

@Des 56
In a nutshell YES!

Question 4 - Answer

Back to basics, heat a volume of air up and it will expand, lets assume no-one lives in a sealed chamber thus air will not build up pressure but simply leave the room where possible, the air that leaves is directly proportional to the expansion effect by the heating of the air thus the overall energy level of the air in the room remains the same.


Its late so ill post another question tomorrow.

 

[Kamikaze]

Time to waffle some more nonsense from this feeble brain of mine

The air is warmed,the warm air has greater volume,air now needs to vacate the premises or the premises needs to get bigger
The volume of the warmed air is more energetic than previous, but, because there is less of it, the total energy remains the same

Air heats up relatively quickly because air is a gas and has relatively little mass. If the room is cold the air will appear to heat up quickly but once the heating process has stopped it will cool down pretty fast too for the same reason. Air by itself doesn't have the ability to store much energy and the energy input far exceeds the energy actually stored but there definitely is an increase of stored energy because electrons can absorb this energy but admittedly a small one. Since we don’t know the rooms volume, the amount of heat that has been radiated into the room and the stand still air velocity, we can not calculate the increase.

 

[Darkwood]

@Kamikaze ..Back to school for you I'm afraid, Air is a poor conductor of heat for the very reason its a gas, its convection of the air over the radiator that warms the passing thin layer up in a repeat cycle thus gradually heating the room up, if air was a good conductor then your tea would go cold very quickly. This is why air acts as a very good insulator and you find many thermal insulators have thousands of trapped air pockets giving them their insulating proporties.

 

[Kamikaze]

@Kamikaze ..Back to school for you I'm afraid, Air is a poor conductor of heat for the very reason its a gas, its convection of the air over the radiator that warms the passing thin layer up in a repeat cycle thus gradually heating the room up, if air was a good conductor then your tea would go cold very quickly. This is why air acts as a very good insulator and you find many thermal insulators have thousands of trapped air pockets giving them their insulating proporties.

That’s why my school reports kept saying “Must try harder” and “Don’t let him lick the wire”. But I’m just a victim of liberal style over scientific substance. What really hurts is that Des has stolen all the glory again.

 

[Des 56]

That’s why my school reports kept saying “Must try harder” and “Don’t let him lick the wire”. But I’m just a victim of liberal style over scientific substance. What really hurts is that Des has stolen all the glory again.

What should hurt is that I have little to no idea about that subject.I suppose my guess trumped you're own undisputed knowledge of physics,anyway,the question was all a load of hot air, now go to the back of the class

 

[Darkwood]

Question 5 -A Weighty problem.

An Aquaduct (as in a bridge carrying water), is used as a canal, when a canal boat rides over the bridge will the bridge be subject to more weight..ie does the bridge need to be designed to carry the boat as well as the water?

 

[David M]

No, In order for any thing to float an object must displace a volume of water heavier than the actual object. So my guess is, in this scenario as the boat passes over the bridge the actual load on the bridge may even reduced slightly.

 

[Wilko]

Boat displaces its own weight in water and since its an open ended canal (and not a bath) the displaced water moves out along the canal in all directions. So that's a "no" from the rubber duck

 

[Kamikaze]

Eureka! I actually know the answer to this one because I studied Greek scientists and philosophers at the alma mater and the person that solved that particular problem was a personal favourite of mine.

 

[static zap]

Eureka!...... was a personal favourite of mine.

In a streak of inspiration