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Engineering Dynamics

  1. Sep 7, 2015 #1
    1. The problem statement, all variables and given/known data
    The 160-Mg train travels with a speed of 80 kmlh when it starts to climb the slope. If the engine exerts a traction force F of 1120 of the weight of the train and the rolling resistance F D is equal to 1/500 of the weight of the train, determine the deceleration of the train. slope is y=1 and x=10 Capture.PNG

    ****See attached files for picture.
    2. Relevant equations
    I summed the forces in the x and y directions because it is going up a slope.

    3. The attempt at a solution
    the solution I keep getting is in the right direction, but is 1.0m/s^2 off. i.e. -1.5m/s^2 roughly.
     
  2. jcsd
  3. Sep 7, 2015 #2
    The engine exerts a traction force of F(1/20) of the weight of the train. Not 1120
     
  4. Sep 7, 2015 #3

    vela

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    Show your work. Simply telling us the wrong answer you got isn't very helpful in seeing where you might have gone wrong.
     
  5. Sep 7, 2015 #4
    ∑F(x)=Fcos(5.7)-F(Resistance)cos(5.7)-F(Normal)cos(84.3)-mg*cos(84.3)=ma
    ∑F(y)=Fsin(5.7)-F(Resistance)sin(5.7)+F(Normal)sin(84.3)-mg*sin(84.3)=ma

    I uploaded a free-body diagram.
     

    Attached Files:

  6. Sep 8, 2015 #5

    vela

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    Can you explain your reasoning behind the equations?
     
  7. Sep 8, 2015 #6
    Well I wanted to prove that the axis didn't need to be rotated. It certainly makes things easier if you do, but I wanted to break everything down into components to get a better understanding of how all of the forces are represented in the problem by using vectors. I want a fool proof way to begin dynamics. I did the above equation way wrong. I didn't give acceleration components for x or y most importantly.

    I'm just trying to find a common approach to problems. Pulleys are different.
     
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