Find tension of string in a pendulum

  • Thread starter Jtappan
  • Start date
  • #1
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Homework Statement



A pendulum is 0.615 m long and the bob has a mass of 1.37 kg. When the string makes an angle of =14.1° with the vertical, the bob is moving at 1.40 m/s. Find the tangential and radial acceleration components and the tension in the string. [Hint: Draw an FBD for the bob. Choose the x-axis to be tangential to the motion of the bob and the y-axis to be radial. Apply Newton's second law.]
at = _____m/s2
ar = _____ m/s2
T = _______ N

Homework Equations



F=MA

The Attempt at a Solution



I have tried breaking up the forced using the FBD but I cannot get the right answer for any of them. I have no idea what I am doing wrong. For the tangential acceleration i got: 6.54 and 6.74 doing it two different ways. For tension I got 13.02 N and those are still not correct...
 

Answers and Replies

  • #2
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In the y (radial) direction there is T and a component of gravity.
In the x (tangential) direction, there is only the other component of gravity.

So figure out Fnet in the tangential direction then Fnet in the radial direction.
 

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