Problem with forces on a ramp

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  • #1
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Homework Statement


A luggage handler pulls a suitcase of mass 16.3 kg up a ramp inclined at an angle 22.0^\circ above the horizontal by a force F of magnitude 147 N that acts parallel to the ramp. The coefficient of kinetic friction between the ramp and the incline is 0.264. The suitcase travels a distance 4.15 m along the ramp.

Find work done by force F, gravity, friction, the normal force, and the total work done on the suitcase.

Also, if the speed of the suitcase is zero at the bottom of the ramp, what is its speed after it has traveled 4.15 m along the ramp?


Homework Equations





The Attempt at a Solution


https://lh3.googleusercontent.com/_...AALs/IzFXWo-6lAE/s800/IMG_20110312_000306.jpg
 
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Answers and Replies

  • #2
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Well, since the work is the integral of the force, once i get the force i just use the fnint() function on my ti-83 to find the work...so i didn't write it out. so if i can find the correct force, the work is easy to find. but something is wrong with my forces. but thanks for being a jackass. i really appreciate your condescending attitude towards people who are just asking for help on a forum designed to help people with these sorts of things...

and just in case you need this too, here's the page where i tried to find velocity. and i even wrote out a generic integral on here so you know what i did..

IMG_20110312_151608.jpg
 
  • #3
PhanthomJay
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When you took the sum of forces in the x direction, you assumed that the acceleration was 0. This is not necessarily the case. You can use Newton 2 in that direction to solve for the acceleration. However, this question is not asking for the acceleration.
Once you identify all the forces, which you have done, and the magnitude and direction of these forces, you can find the work done by each. You don't need the calculus to do so when forces are constant....but you need to watch plus and minus signs and use the dot product rule for work done by a force.

Then, the work energy theorem states that the sum of the work done by ALL forces is the kinetic energy change. You must add them all up first before calculating the speed.
 

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