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: Shm correct?

  1. Sep 15, 2009 #1
    1. The problem statement, all variables and given/known data
    The pistons of a 4 cylinder car engine when idling move approx. in SHM with an Amplitude of 50mm and at a frequency of 110Hz.Calculate
    *the max speed of the pistons.
    *max acceleration of the pistons.

    2. Relevant equations
    max velocity = A(omega),max acceleration =A(omega)^2, omega= 2pie/T,T=1/f

    3. The attempt at a solution
    for the first bit i did:
    =>0.05x2(pie)/9.09x10^-3 (from T=1/F)
    => 34.56m/s.
    The second bit is simply
    =>0.05 x (34.56)^2
    => 59.71m/s^2
    hm.. is this how i am supposed to do it ? :)
    Thanks in advance.
  2. jcsd
  3. Sep 15, 2009 #2
    Your method is fine but you have substituted the wrong value for omega in the second part of the problem. Just correct it and add a minus sign in the formula for acceleration.
  4. Sep 15, 2009 #3
    ermm i thought for max acceleration the formula was:A(omega)^2 and for acceleration a=-A(OMEGA)^2cos(omega)t... maybe (confused) =/
  5. Sep 15, 2009 #4
    Yeah, you are right. In fact, it's the same thing.

    The thing I wanted to point out was that you substituted the speed you calculated instead of the angular frequency (omega) in that second part of the problem.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook