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Homework Help: Calculating how fast a motor can move something in horizontal motion

  1. Sep 17, 2011 #1
    1. The problem statement, all variables and given/known data
    So I need a motor for a project. The motor i'm looking at creates circular motion. I want to make the motor move some object in a horizontal motion but I want to know how fast it can move the object horizontally before getting it. How can I find out how fast the motor can move it?
    Motor in mind:
    http://www.servodatabase.com/servo/hitec/hs-322" [Broken]

    Sorry if there are unnecessary unit conversions. Seems like engines are explained in imperial units.

    2. Relevant equations

    Using this equation to find horsepower = (Torque x Engine speed (rpm)) / 5,252 = Horsepower
    Found from:http://www.howstuffworks.com/question622.htm"

    Torque for engine = 3.70 kg*cm = 0.03 kg per m = 0.22 lb/ft

    speed = 0.15 sec/60° (not really sure what this is? Assuming 60 degrees every .15 sec. So one revolution (360 degrees) = 0.15 sec x 6 = .90 sec. Then rpm = 66.7

    Mass of object being rotated =0.2 kg

    3. The attempt at a solution

    One way I thought of calculating this was converting the torque output to Power then converting power to work then to kinetic energy to velocity.

    Horse power = 0.22 * 66.7 /5252 = .0028 horse power

    Mechanical horse power = 33,00 lb*ft/min so (0.028 * 33,000)/60s= 1.54 lb*ft =2.09 n*m

    I'll assume all work will equal KE. 2.09 J = 0.5 *0.2*v2

    V= 4.6m/s.
    Does it look right? Any help would be appreciated.
    Last edited by a moderator: May 5, 2017
  2. jcsd
  3. Sep 17, 2011 #2

    rude man

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    Homework Helper
    Gold Member

    Think about this: you said 'horizontal' motion. What if anything limits the velocity if you continually apply a certain amount of power to a mass moving horizontally?

    BTW on the rhs equation of 'mechanical horse power' the dimension is energy, not power, so I would check that. Always check dimensions on any work you do. Every single term. I find more mistakes I make that way than with any other, by a mile!
  4. Sep 17, 2011 #3
    I'm guessing you mean drag and friction? Would it still affect it a lot with the device being so small? I don't think I would be able to calculate it with the information I'd have.

    Sorry isn't it in energy already? 2.09 Nm is Joules.
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