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Homework Help: Velocity attained by sled

  1. Oct 18, 2003 #1
    OK i'm stuk on a physics question involving Newton's Laws of motion.


    Boy gives his sister ride on sled by exerting force of 300 N[E].
    Frictional resistance amounts to 200 N. If sister and sled have combined mass of 50 kg, and if boy starts from rest and pushes for 5 sec., find:

    a) the sled's acceleration
    b) velocity attained by sled in 5 sec.
    c) distance travelled by sled in 5 sec.

    PLZ try to help and show step by step solutions

    Reply ASAP thanx:smile:
  2. jcsd
  3. Oct 18, 2003 #2


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    Science Advisor
    Gold Member

    It's not the policy here to do peoples homewrok, but I'll give you the relevant formulae:

    F = ma, v = u + at, s = ½(u + v)t

    F is force, m is mass, a is acceleration ,v is final velocity, u is intial velocity, s is displacemnet and t is time.
  4. Oct 19, 2003 #3

    Wait, how do we find initial velocity?

    Thanx for help.
  5. Oct 19, 2003 #4


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    Science Advisor

    We don't. But since the problem asked for the "velocity attained" (i.e. the increase in velocity), we can take it to be 0- that way the final velocity WILL be the increase in velocity.
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