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Homework Help: Finding power without given speed or time

  1. Dec 7, 2017 #1
    1. The problem statement, all variables and given/known data
    The lawn tractor in figure 18 goes up a hill at a constant velocity. Calculate the power that is developed by the tractor.
    Mass: 120.0 kg
    Angle of incline: 21 degrees
    Distance: 12.0 m
    Velocity: no velocity given other than it is constant
    Time: idk

    2. Relevant equations
    None really

    Just note that I used 9.8ms^-2 for acceleration due to gravity, NO value for velocity was given, and no time value was given.

    3. The attempt at a solution
    So I calculated the force in the direction of down the slop (by using mgsin21) and got a force of 421.4N, which means, since the acceleration in the dimension of the slope is 0ms^-2, that the net force is zero, meaning that the motor produces 421.4N of force. Now from here I’m stuck, as no value for velocity is given other than that it’s constant, and idk how to calculate time without velocity so that I could calculate power. Pls help.
  2. jcsd
  3. Dec 7, 2017 #2


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    Science Advisor
    Homework Helper
    Gold Member

    If that is all you are given then there is clearly not enough information. Make very sure there is no information you have overlooked. Some detail in the figure, perhaps?
  4. Dec 7, 2017 #3


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    Staff: Mentor

    Hi J51mustang,

    Welcome to Physics Forums!

    Since no velocity is given it looks like you'll have to provide a symbolic answer rather than a particular numerical result...
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