Horsepower moving a mass

  • Thread starter RileyAllen
  • Start date
  • #1

Homework Statement


What minimum horsepower must a motor have to be able to drag a 270 kg box along a level floor at a speed of 1.20 m/s if the coefficient of friction is 0.50?


Homework Equations


Ffr=mu*mg
W=Ffr*d


The Attempt at a Solution


I ended up having W=Fr*d=mu*m*g*d
(.5)*(270)*(1.2)*(1.2)=194.4 J/s=.26 hp

That is way too low.

Can anyone give me any guidance?
 

Answers and Replies

  • #2
Delphi51
Homework Helper
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It looks like you just used 1.2 instead of 9.81 in your calc, but it would be better to use P = F*v.
If you don't know this formula, it is from P = W/t = F*d/t = F*v.
 
  • #3
Is the way I tried it wrong? I ended up with hp=2.13 and that still seems pretty low
 
  • #4
Delphi51
Homework Helper
3,407
11
That answer looks good!
Why does it seem low? Picture a pair of horses pulling a sled with a big guy on it at 5 km/hr?
 

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