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Homework Help: Power and work question!

  1. Dec 7, 2012 #1
    1. The problem statement, all variables and given/known data

    65. A 50-N force is the only force on a 2-kg object that starts from rest. When the force has been
    acting for 2 s the rate at which it is doing work is:
    A. 75W
    B. 100W
    C. 1000W
    D. 2500W
    E. 5000W
    ans: D

    66. A 50-N force is the only force a 2-kg crate that starts from rest. At the instant the object has
    gone 2m the rate at which the force is doing work is:
    A. 2.5W
    B. 25W
    C. 75W
    D. 100W
    E. 500W

    Q1 solved but i have no idea how to do the second one!
  2. jcsd
  3. Dec 8, 2012 #2


    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    Look up the standard equations of motion (SUVAT). Some are more useful for problems involving time (eg Q1) and others for displacement (Q2).

    Perhaps this one...

    V^2 = U^2 + 2as

    where s = displacement
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