1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: How longs a peice of string

  1. Mar 22, 2007 #1
    1. The problem statement, all variables and given/known data
    In this case how tights a peice of wire with a ball, at one end and a pivot P at the other. A wire from the pivot P suspends a ball, m.

    Problem:Find T(r) for the values of m, v and g (in terms of r).

    2. Relevant equations

    The tension or force in the wire, T, when the ball m is swinging through the lowest point is given by the function:

    T(r)=mg+(mv^2/r) where m=1.0 kg, v=7.75 ms–1, g = 9.81 ms-2 T is in Newtons

    r is the disrance from the pivot P to the centre of the ball when the wire is stretched.When the wire is not stretched, its length is 2.89m.

    3. The attempt at a solution

    r=-mv^2/mg therefore r=-1x7.75^2/1x9.81 =-6.123m 3dp

    Just wondering if Im on the right track here I dont see how r could be a negative number and if not how can it be twice the length when stretched?
    Last edited: Mar 22, 2007
  2. jcsd
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Can you offer guidance or do you also need help?
Draft saved Draft deleted