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Homework Help: Weight and Free Fall

  1. Sep 26, 2006 #1
    Hey guys, I'm confused about this problem -

    On a planet far, far away, an astronaut picks up a rock. The rock has a mass of 5.80 kg, and on this particular planet its weight is 40.0 N. If the astronaut exerts an upward force of 43.3 N on the rock, what is its acceleration?

    I thought you just did a=1/m*Fnet. The mass is 5.8, and I thought Fnet would be 43.3n+40N but my answer is not coming out right. If anyone could help me out I'd really appreciate it!
     
  2. jcsd
  3. Sep 26, 2006 #2
    What about the direction of the forces? Fnet is a vector sum.
     
  4. Sep 26, 2006 #3
    I wasn't sure about that, I thought maybe -40N because that's it's weight and then the +43.3N because it's being thrown upward but it keeps saying my answer is wrong.
     
  5. Sep 26, 2006 #4
    You're right. It should be 3.3/5.8 ms^-2 (assuming the data is right). May be you didn't provide the answer to the required number of decimal places.
     
  6. Sep 26, 2006 #5
    I got it, I think I may have forgotten to make the 40N negative or something...thanks so much!
     
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