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Homework Help: Relationship between newton's laws and distance

  1. Jul 3, 2010 #1
    1. The problem statement, all variables and given/known data

    a)If the mass of the crate is doubled but the initial velocity is not changed, what distance does the crate slide before stopping? Explain.

    b) If the initial velocity of the crate is doubled to 2vi but the mass is not changd, what distance does the crate slide before stopping? Explain.

    2. Relevant equations

    V2=Vi2 + 2a(Xf-Xi)

    3. The attempt at a solution
    in this case, since the motion is horizontal, I though the X COMPONENT OF THE normal force = 0 and the X COMPONENT of the weight is equal to zero. I tried the problem again and for the condition (2m,v) my new answer is d= (initial velocity squared) (mass)/kinetic friction. ANd for condition (m, 2v) my answer is d= (2 times initial velocity squared) (mass)/kinetic friction. I hope these are correct. Thank you kindly for your help. Also, I know this was posted before but I posted it as a reply and i just want to make sure that this is answered so that is why i started another threat. Sorry for taking up the space but can you please tell me if this is right?
  2. jcsd
  3. Jul 4, 2010 #2
    someone seriously please help!
  4. Jul 5, 2010 #3


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    Staff Emeritus
    Science Advisor
    Homework Helper

    Good, that is the right equation to use to think about this.

    Yes, so far so good. Uh, except the "2" should be "1/2", but that won't really matter here.

    Next step would be to work on the kinetic friction. What is that equal to? (Hint: use the relation between kinetic friction and the normal force.) Can you relate it to the mass of the crate?
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