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Forces & Friction question!

  1. Dec 7, 2012 #1


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    A 5 kg block rests on a 30degree incline
    the coefficient of static friction is between the block and incline is 0.2
    how large a horizontal force must push on the block if the block is to be on the verge of sliding a)up the incline and b) down the incline

    So far I have ma=Fapp-(m)mg-mgsin30
    where (m) is miu or friction co-efficient

    ive been working on this for a long time but not sure how to get the answers
    any help will be much appreciated!
  2. jcsd
  3. Dec 7, 2012 #2

    Simon Bridge

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    Welcome to PF;
    Would you be able to do this if the block were not on an incline?

    So far you have ##ma=F_{app}-\mu_kmg - mg\sin{\theta}## (resist the urge to put the numbers in so soon).

    Is this for pushing the block up or down the slope?
    Which direction does friction act?

    According to the description: what is the acceleration?
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