Ok..today i'm gonna answer my previous question on hot air balloon...some of u did answer it with some common sense on why the balloon rises easily in the early morning..
However in SPM, using common sense only isn't enough for u to get full mark..u must relate your answer with relevant physics concepts or principles.
...Physics concept??? What physics concept???
To make it simple, if hot air balloon rises, it needs a larger force pulls it up to counter its weight that pulls it down.
In SPM, this upward force is called buoyant force..atau in bahasa melayu we call it 'daya apungan'.Thats why the balloon can rise & float, coz ada 'force' yang tolong mengapungkannya. So the question is how to have this 'daya apungan' big enough to pull the baskets??
This buoyant force concept comes from a famous principle called 'Archimedes Principle'.Now, lets analyse how can we can relate it to this principle...
Archimedes Principle
Mr Archimedes states that...
If an object is fully / partially immersed in a "FLUID" the buoyant force is equal to the weight of the fluid displaced.
The term 'fluid' is used in the statement above..do u understand what fluid is? Senang cerita fluid ni adalah benda yang mengalir such as liquid & gas. In the case of hot air balloon, the object is the balloon. The fluid is the surrounding air ( udara) which is the one that was displaced.
THEN according to archimedes principle..we can deduce a formula like this:
Buoyant force = Weight of AIR displaced ( since W=mg)
Buoyant force = mg [(mass of air displace ) x (g)]
(since density ρ = m / V , so m = ρV)
Therefore,
Buoyant force = ρVg (air displace)
( ρ =density, V =volume)
From the formula, Buoyant force depends on the air density.
We can say that the bigger the density, the larger the buoyant force...
Ok this is the key factor to determine the right time for hot air balloon to take off .
..
Early in the morning, the air is cooler than in the afternoon. Cooler air is denser than hot air, i.e it has higher density. According to the relationship above, cooler air will result in bigger buoyant force. So the balloon has a larger buayant force to counter its weight. Thus the balloon will be easier taking off in a cool temperature rather than during hot tempperature. This explain why the organiser choose those two session, i.e early in the morning and in the evening.
Another point,when buoyant force is bigger, so we can carry more loads. Thus if the same no of 'burners' is used,more participant can be carried in the morning compared to afternoon.
Please noted this discussion is only concerned about the air density surrounding outside the balloon.
There are many other factors that allow the balloon to rise faster..so its your task to figure it out yourself :)
haha ni ada sikit clue, cuba u all masak maggi, then observe..asap dia naik ke turun :) ????
tapi kalau bukak freezer peti ais cuba tgk asap dia naik ke turun??
May b u can also try this activities at home..
May b u can also try this activities at home..
8 comments:
I went to laut mati and I was floating(Last time I went to normal sea I sank). Is it my buoyant force is equal to the weight of the fluid displaced?
of course buyant force is always = weight of liquid displaced regardless whether u float or sink.
U r floting in laut mati coz it has higher density than other sea water.Buoyant force dpends on liquid density, thus laut mati produce larger buoyant force. When this buoyant force is bigger or equal to yr weight, than u r able to float
cikgu,may i ask?why is it when somebody is drowning in the sea for example,he does'nt float?suppose to be when he is less dense than seawater he will float,but then why later on he sinks?or is it bcoz the water absorb by his cloth probably makes him drown?
well there are several factors,like cntre of gravity which we dont cover it in details for spm..
however still u cn apply archimedes principle to enable a person to float or sink..
basically density of the human body is either higher or lower than water. The difference might be determined by how much air they have in their lungs. People can generally float if he displaced enough water to create the buoyancy. If you are underwater, however, and you exhale enough of your air, you will sink.
In fact our body itself is filled with liquid,fat & so on..& they might also becomes one of the factor why we sink or float. May be u should also wonder why dead people float???
I am doing research for my university paper, thanks for your excellent points, now I am acting on a sudden impulse.
- Kris
SIR, can you give 2 example question for archimedes principle with it answer. :)
Fluid dalam bm adalah bendalir, kan?
Fluid dalam bm adalah bendalir, bukan?
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