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Homework Help: Just need the formulas please

  1. Oct 23, 2007 #1
    1. The problem statement, all variables and given/known data:

    #1. You are walking on a perfectly round asteroidwith a diameter of 40km and a mass of 10 to the 16th kg. your mass is 60kg. how much will you weigh, in Newtons?

    #2 a 100 kg porshe is moving at a steady speed around a cicular track waith a 1000 m radius. The porshe's centripedal acceleration is 5 m/s squared. What is teh magnitude of its velocity?

    2. Relevant equations

    3. The attempt at a solution

    I tried a=v squared/r but it doesn't include the mass so i didn't think it's right and i've looked through all my notes and can't find a formula for the second one. For the first one i'm lost cause f=ma dont work. any help i would be grateful for, thanks.
  2. jcsd
  3. Oct 23, 2007 #2


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    You are on the right track for the second one, and you don't need the mass. On the first one look up Newton's law of gravitation.
  4. Oct 23, 2007 #3
    thank you very much. after i get 71 for the second answer how do i change it into km/hr
  5. Oct 23, 2007 #4


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    Put units on things, ok? If you got 71m/sec and you really want to convert to km/hr, then 1m=km/1000 and 1sec=hr/3600. Now what? Units are your friends, they help you from being confused.
  6. Oct 23, 2007 #5
    Thanks for the help.
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