Dismiss Notice

Welcome To CK5!

Registering is free and easy! Hope to see you on the forums soon.

Score a FREE t-shirt and membership sticker when you sign up for a Premium Membership and choose the recurring plan.

Need Help with Two more quick physics questions.

Discussion in 'The Lounge' started by colbystephens, Mar 2, 2006.

  1. colbystephens

    colbystephens 1 ton status GMOTM Winner

    Joined:
    Feb 24, 2005
    Posts:
    10,924
    Likes Received:
    20
    Location:
    Oregon
    1. what are the units of a watt?
    2. a certain car battery with a 12.0 v emf has an initial charge of 120 Amp Hours. Assuming that the potential across teh terminals stays constant ntil the battery is completely discharged, for how many hours can it deliver energy at the rate of 100W?
     
  2. neverendingproject

    neverendingproject 1/2 ton status

    Joined:
    Jul 24, 2005
    Posts:
    1,637
    Likes Received:
    0
    Location:
    Tulsa, OK
    watt=volts*amps
     
  3. ryan22re

    ryan22re 1/2 ton status

    Joined:
    Feb 5, 2005
    Posts:
    3,368
    Likes Received:
    0
    Location:
    Irmo, SC
    p=ir

    watts = volts x amps

    right?
     
  4. colbystephens

    colbystephens 1 ton status GMOTM Winner

    Joined:
    Feb 24, 2005
    Posts:
    10,924
    Likes Received:
    20
    Location:
    Oregon
    cool thanks. the answer in my book says 14.4 hours. seems like it should be exactly 14 tho. 12x120/100=14. any ideas?
     
  5. readymix

    readymix 3/4 ton status

    Joined:
    May 30, 2004
    Posts:
    6,706
    Likes Received:
    26
    Location:
    Murrieta, California
    A watt is one Volt Amp, if that is what you are asking

    14.4 hours, Don't quote me though
     
  6. readymix

    readymix 3/4 ton status

    Joined:
    May 30, 2004
    Posts:
    6,706
    Likes Received:
    26
    Location:
    Murrieta, California
    I got 14.4 from my calculations
     
  7. colbystephens

    colbystephens 1 ton status GMOTM Winner

    Joined:
    Feb 24, 2005
    Posts:
    10,924
    Likes Received:
    20
    Location:
    Oregon
    can you explain the 14.4 - i end up with 14. i must be missing something pretty simple. oh crap. i just realized i can't multiply. 12x12=144, not 140. thanks, all.
     
  8. readymix

    readymix 3/4 ton status

    Joined:
    May 30, 2004
    Posts:
    6,706
    Likes Received:
    26
    Location:
    Murrieta, California
    100W / 12Vdc = 8.333333333A
    120 AH / 8.33333333 = 14.4Hrs


    Make sense??
     
  9. colbystephens

    colbystephens 1 ton status GMOTM Winner

    Joined:
    Feb 24, 2005
    Posts:
    10,924
    Likes Received:
    20
    Location:
    Oregon
    yes, it makes sense now. i'm an idiot. and i can't multiply.
     
  10. Jagged

    Jagged 1 ton status

    Joined:
    Apr 25, 2005
    Posts:
    11,460
    Likes Received:
    1
    Location:
    SWVA
    Well, that sounds like a personal problem.
     

Share This Page