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!

Particle at rest; v(t) = 0

  1. Oct 28, 2013 #1
    (1.)

    I have a "particle in motion" problem that is asking me when a particle is at rest, which I understand to be when velocity = v(t) = 0, so

    v(t) = - (π/4) sin (πt/4) = 0.

    The given answer is as follows:

    - (π/4) sin (πt/4) = 0

    sin (πt/4) = 0

    πt/4 = πn.

    t = 0,4,8 seconds.

    (2.) Can someone please explain to me how 0 becomes πn, and/or what specific mathematical concept(s) I need to review?
     
  2. jcsd
  3. Oct 28, 2013 #2

    vanhees71

    User Avatar
    Science Advisor
    2016 Award

    What's the full problem statement?

    Of course [itex]\sin(n \pi)=0[/itex] for all [itex]n \in \mathbb{Z}[/itex].
     
  4. Oct 28, 2013 #3
    The full problem statement goes:

    A particle moves according to a law of motion s = cos(πt/4), t >= 0, where t is measured in seconds and s in feet.

    There are several sub-questions from here about velocity, acceleration, graphs, etc.., but the one that I got stuck on is

    (c.) When is the particle at rest for t <= 10.

    After differentiating the given function for f', understanding the answer to this question was as simple as reviewing the unit circle and the graph of sin for me, as elementary as it may be.

    Thank you for your time!
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted



Similar Discussions: Particle at rest; v(t) = 0
  1. TT'(t) - cT(t) = 0 (Replies: 6)

  2. Curl(V) = 0 (Replies: 3)

  3. Curvature When t=0 (Replies: 5)

Loading...