1. Not finding help here? Sign up for a free 30min 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!

Acceleration of a revolving ball

  1. Aug 14, 2009 #1
    1. The problem statement, all variables and given/known data

    A 150-g ball at the end of a string is revolving uniformly in a horizontal circle of radius 0.600m. The ball makes 2.00 revolutions in a second. What is the centripetal acceleration?

    2. Relevant equations

    T = 1/f
    v = 2[tex]\pi[/tex]r / T


    3. The attempt at a solution

    I know the answer to this question because its an exercise but I am confused with the "T" equation (Period equation).

    v = 2[tex]\pi[/tex]r / T

    v = 2(3.14)(0.600m) / (0.500s)

    How did we get the 0.500s?
     
  2. jcsd
  3. Aug 14, 2009 #2
    If in one second, the mass completes two revolutions, how long does it take for it to complete one revolution?

    The relationship between the frequency (How many occurrences per unit of time) and the period (How long it is between one occurrence and the next) is:
    [tex]f=T^{-1}=\tfrac{1}{T}[/tex]
     
  4. Aug 14, 2009 #3

    tms

    User Avatar

    From the statement of the problem. If the ball makes 2 revolutions in one second, how much time does it take to make one revolution?
     
  5. Aug 14, 2009 #4

    Delphi51

    User Avatar
    Homework Helper

    F = ma = m*v^2/R
    cancel the m's to get a formula for acceleration.
    There is an alternative one where v is replaced by 2*pi*R/T
     
  6. Aug 14, 2009 #5
    so basically:

    f = 2.00s -1 = 0.500s.

    I think the extra zero's confused me.
     
  7. Aug 14, 2009 #6

    tms

    User Avatar

    You got the right answer numerically, but you got it by confusing the frequency. The correct expression for the frequency is

    [tex]f = 2.00 \: \frac{1}{\text{sec}},[/tex]

    while you seem to have used

    [tex]f = \frac{1}{2.00 \:\text{sec}}[/tex]

    and then fudged the units in the result.

    They shouldn't. You should always keep the right number of significant digits in your calculations.
     
  8. Aug 15, 2009 #7
    Like tms said, the dimensions for frequency are [tex][T]^{-1}[/tex], and its units in the MKS system are [tex]\tfrac{1}{sec}\equiv 1 Hz[/tex]
    1 Hz (1 Hertz) is defined as a frequency of 1 per second.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Acceleration of a revolving ball
  1. Acceleration of a ball (Replies: 3)

  2. Accelerating Ball (Replies: 6)

Loading...