physics

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i know how to do it, i keep getting the wrong answer!!

a bob of mass 4.00 kg is suspended from a fixed point by a massless string of length 1.50 m. The bob moves in a horizontal circle with the string always making an angle theta=22 from the vertical. what is the speed of the bob?

(tension is 42.3 N)

  • physics -

    Look at the tension:
    tension=mg/sinTheta
    Now, the horizontal component of tension is tension*costheta, or mg/tantheta

    That must equal centripetal force,
    mv*2/radius.
    the radius must be 1.50*sinTheta

    so finally,
    mv^2/1.5*sintheta =mg/tantheta
    solve for v
    check my thinking.

  • physics -

    thank you so much!! it was so frustrating to get the wrong answer after wrong answer..

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