soalan simple

musang_pulut

Originally posted by prototaip at 8-2-2007 04:09 PM
Lagi satu,

jisim kayu + jisim oksigen = jisim carbon + jisim carbon dioksida

tenaga pembakaran + tenaga ikatan dalam kayu =tenaga ikatan dalam carbon + tenaga ikatan dalam carbon dioksida + ...

Aku tambah sikit..

Dinding sel tumbuhan (kayu) dibuat daripada selulosa. Selulosa,  (C5H10O5) n terbina dari rantaian molekul panjang, polisakarida yg memberi sokongan pada pokok. Selulosa pula merupakan gabungan monomer glukosa. Kalau tgk balik formula molekul selulosa terdiri daripada C, H dan O. Apabila berlaku pembakaran kayu, tenaga dibebaskan dalam bentuk cahaya dan haba. Dengan kehadiran oksigen semasa proses pembakaran, C bertukar kepada carbon monoxide dan carbon dioxide. Hidrogen yang terhasil akibat pemecahan rantaian akan membantu proses pembakaran...

kayu + udara + tenaga haba -----> debu + asap + tenaga haba

CH2O(s) + O2(g) -----> CO2(g) + H2O(g)

Dari mana plak datang asap...

Pembakaran lengkap selulosa membebaskan sama ada debu atau asap. Kayu juga mengandungi mineral tidak terbakar yang menghasilkan debu selepas pembakaran. Jika sekiranya jumlah oksigen tidak mencukupi untuk melengkapkan proses pembakaran, asap akan dihasilkan.

CH2O(s) -----> C(s) + H2O(g)

[ Last edited by  musang_pulut at 12-2-2007 10:55 AM ]

reinloch

For the first question,
a person exerted himself to loosen a screw which would not budge.
The question involves where the products of that exertion went.
As force is exerted on the spanner, equal reactive force results. Since the screw was tightened to a great extent with a presumably large amount of force applied, the force required to budge the screw would be similar. In the stable screw and nut frame of reference, when the human force is exerted, the reactive force causes a zero vector sum hence zero acceleration and no movement. Body heat is a byproduct of the inefficient human engine, and sweat is a byproduct of inefficient heat dissipation mechanism.   


For the second question,
if we light a match. where does the mass go?
Will it be destroyed or changed to a different form?
If it does change form, what is the new form and is it related to energy that cannot be created or destroyed?
The process of burning a sliver of wood naturally invokes a rearrangement of atoms as evident in balanced chemical equation. However, it is only rearrangement and not change since only fusion or fission unlocks atomic change. In this perspective, the total mass of the system remains presumably the same assuming the co2 and h20 does not leave the system. Incomplete combustion yields carbon remains evident from the wood ashes. But, as checimal potential energy radiates out of the system as kinetic energy in ir waves transmitting heat, the system is losing mass in the form of energy. This loss is relatively minuscale hence the earlier presumption.

seladanganas

kalau ngko suka melihat kerja dari sudut fizik, ngko boleh bayangkan bila ngko nak membuka nut/ bolt tu dgn spanar, jantung yg bertindak sbg pam hidraulik mengepam dgn lebih laju dan aliran darah bertambah. kerja terjadi bila satu bentuk tenaga berubah menjadi tenaga lain. cthnya enjin kereta menukar tenaga kimia dari petrol kpd tenaga mekanikal, tenaga haba dan bunyi. bayangkan kereta yg baru dihidupkan, tidak bergerak. pada matra kasar tiada kerja dilakukan tapi pergerakan selinder dlm enjin case turun naik melakukan kerja. begitu juga tubuh kita membakar glukos yg dibawa oleh aliran darah. pergerakan cecair didalam sel2 tubuh kita hg jumlahnya beberapa trillion juga boleh dikatakan kerja fizikal. aliran isyarat letrik dari otak utk mengerakan otot tangan juga satu kerja dlm bentuk letrik. kerja juga bolehdikira dgn formula lain contohnya bagi pengembangan gas pressure  x volume. bila ngko bernafas paru2 kembang kuncup juga satu bentuk kerja yg boleh di kira dgn formula diatas.

ussopp

Originally posted by reinloch at 13-2-2007 12:02 PM
For the first question,
a person exerted himself to loosen a screw which would not budge.
The question involves where the products of that exertion went.
As force is exerted on the spanner, equal reactive force results. Since the screw was tightened to a great extent with a presumably large amount of force applied, the force required to budge the screw would be similar. In the stable screw and nut frame of reference, when the human force is exerted, the reactive force causes a zero vector sum hence zero acceleration and no movement. Body heat is a byproduct of the inefficient human engine, and sweat is a byproduct of inefficient heat dissipation mechanism.   

ooo...patut pun
tenaga aku tak equal lagi ngan tanaga masa orang ketatkan skru tuu...
apsal laa dia ketatkan kuat sangat

anyway thanks for da reply..k

[ Last edited by  ussopp at 18-2-2007 03:56 PM ]

ussopp

Originally posted by seladanganas at 18-2-2007 05:03 AM
kalau ngko suka melihat kerja dari sudut fizik, ngko boleh bayangkan bila ngko nak membuka nut/ bolt tu dgn spanar, jantung yg bertindak sbg pam hidraulik mengepam dgn lebih laju dan aliran darah ...

yaya ke sini rupanya tenaga aku pergi...

kini memang aku tau laa...walaupun tak ada effect kt skru, tapi kt badan aku banyak effect...

nampak mcm tak jadi apa2 tapi banyak bende yg jadi

yg jadi dlm badan pun dah cukup kompleks dah..


thanks for your reply...

p.s : pasni bila aku pulas nut lagi , makin lama la kot, sebab nak pikir mcm2..hehe...

meitantei

Originally posted by reinloch at 13-2-2007 12:02 PM
For the second question,
if we light a match. where does the mass go?
Will it be destroyed or changed to a different form?
If it does change form, what is the new form and is it related to energy that cannot be created or destroyed?
The process of burning a sliver of wood naturally invokes a rearrangement of atoms as evident in balanced chemical equation. However, it is only rearrangement and not change since only fusion or fission unlocks atomic change. In this perspective, the total mass of the system remains presumably the same assuming the co2 and h20 does not leave the system. Incomplete combustion yields carbon remains evident from the wood ashes. But, as checimal potential energy radiates out of the system as kinetic energy in ir waves transmitting heat, the system is losing mass in the form of energy. This loss is relatively minuscale hence the earlier presumption.

Tak benar jugak... Sebenarnya dlm apa2 tindakbalas kimia, ada mass defect ikut formula Einstein E=mc^2. Tapi masalahnya jisim yg hilang ni kecik sgt sampai boleh aje kita ignore. So mass yg hilang tu ditukar kpd Energy...