1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Stored energy in a battery

  1. Jan 16, 2008 #1
    1. The problem statement, all variables and given/known data
    A certain lead acid storage battery has a mass of 30kg, Starting from a fully charged state, it can supply 5 amperes for 24 hours with a terminal voltage of 12 V before it is totally discharged. a If the energy stored in the the fully charged battery is used to lift the battery with 100% efficiency what height is attained? Assume that the acceleration due to gravity is 9.88 m/s/s and is constant with height. b. If the energy stored is used to accelerate the battery with 100% efficiency what velocity is attained. C Gasoline contains about 4.5 x 10^7 j/kg. Compare this with the energy content per unit mass for the fully charged battery.

    2. Relevant equations

    3. The attempt at a solution

    I don't have an attempt to the solution manly because I am at lost to where to begin. I've read the section this question is referring to over and over again and I can't seem to get any closer to solving this problem. Can anyone please give me a hint on how to solve such a problem?
  2. jcsd
  3. Jan 16, 2008 #2


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    It's just an energy problem. Start by calculating how much energy is delivered in total by a 5 A current at 12 V over 24 hours. Then, figure out the equivalent altitude where the 30 kg battery has that same amount of gravitational potential energy as was released in the form of electricity.

    - Warren
  4. Jan 16, 2008 #3
    Thanks a lot. I ended up with 17.6 km for the height and 587 m/s for the velocity question. I'm still confused on part c. It's been about 3 years since i've taken physics I and II, so i'm trying to recall old information, but it's hard.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook