Advanced Physics Help Needed [update]

• WoAiMeiMei

  27 Mar 08, 20:30

  ahhh i cant get it >__<

• WoAiMeiMei

  28 Mar 08, 20:03

  i got it, using

   

  
  4/3 pi r^3 x density of air x (g - acceleration) = mg
  
  negative accerleration as its in the opposite direction of g

   

  the (g-acceleration bit) is just 9.81 - (the upward acceleration)

   

  awesome : D

• eagle

  28 Mar 08, 20:20

  btw what engineering you taking?
  
  I will be busy till 9th April... After which I will have slightly more air to breathe... Details in crapbox...

• WoAiMeiMei

  28 Mar 08, 20:33

  completed all the pressure/fluid questions..

  just the first 3 questions left >___<

• WoAiMeiMei

  28 Mar 08, 20:34

  ok i was originally going to do mechatronics, but i heard it's not as in demand as civil (every1 needs). but civil looks pretty boring.

   

  i may do mechanical. but mechatronics... it could be in greater demand in the future.

• eagle

  29 Mar 08, 08:32

  Originally posted by WoAiMeiMei:

  ok i was originally going to do mechatronics, but i heard it's not as in demand as civil (every1 needs). but civil looks pretty boring.

   

  i may do mechanical. but mechatronics... it could be in greater demand in the future.

  yup... I like mechatronics... But I think NUS didn't offer it last time..., so I took the next best choice of EE. Now I not so sure...

• WoAiMeiMei

  29 Mar 08, 17:56

  great! u can help with my electrical unit. i dun really like it >__<

• WoAiMeiMei

  29 Mar 08, 18:32

  2 more left >_<

   

• WoAiMeiMei

  29 Mar 08, 18:37

  - completed

• WoAiMeiMei

  29 Mar 08, 18:40

  -edited

• WoAiMeiMei

  5 Apr 08, 10:50

  i cant do this question! >_<

   

  A steel rod is 2.894 cm in diameter at 23.00°C. A brass ring has an interior diameter of 2.887 cm at 23.00°C. At what common temperature (in Celsius) will the ring just slide onto the rod? Give your answer to four significant figures. The linear expansion coefficient of steel is 11.00 x 10^-6 /C°. The linear expansion coefficient of brass is 19.00 x 10^-6 /C°.

• eagle

  5 Apr 08, 12:49

  

  I guess for you, it is probably the algebra that killed you. We use the above equation because we consider the linear expansion of the diameter.

  the ΔT is the same for both, final diameter D is also same for both
  Let As = linear expansion coefficient of steel
  Ab = linear expansion of coefficient of brass

  and ΔLs for steel is ( D - 2.894 )
  ΔLb for brass is ( D - 2.887 )

  rearranging the above equation
  ΔT for steel is (D - 2.894)/(2.894*As)
  ΔT for brass is (D - 2.887)/(2.887*Ab)

  since ΔT is the same for both, equating

  (D - 2.894)/(2.894*As) = (D - 2.887)/(2.887*Ab)

  Solving for D should give us the answer.