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Homework Help: Harmonic Motion Problem

  1. Mar 26, 2016 #1
    1. The problem statement, all variables and given/known data
    A pendulum swings at 70 cycles per minute.

    a. What is the frequency in Hz?

    b. What is the period in seconds?
    2. Relevant equations
    T = 1 / f
    3. The attempt at a solution
    For part a) Used the answer for part b & I took the equation above, divided 1 by 1.167 cycles/second & got 0.85 Hz
    For part b) What I did was divide 70 cycles by 60 seconds to get 1.167 cycles/second

    I feel like I did it correct but I had gotten it wrong when the teacher had graded my work.
  2. jcsd
  3. Mar 26, 2016 #2
    You got it wrong because you're mixing up the definitions of frequency and period.

    Also, in general, problems that are ordered by parts are usually done so logically, meaning that you use part A to help you solve part B. The fact that you felt the need to do it backward should have been a sign you were maybe doing something wrong.

    It is also good practice to use information given by the questions to your advantage. For example, in part B, the questions asks "What is the period in seconds" meaning the answer should be seconds. Your answer is in cycles/second, which means your answer is wrong.
    Last edited: Mar 26, 2016
  4. Mar 26, 2016 #3
    You have to understand first what is given, is it frequency or period? After that, you can correctly answer the questions.
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