Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Moment calculation with levers

  1. Feb 4, 2009 #1
    Hi everyone, my name is Alex. Im a Kinesiology major and taking a biomechanics course which has a lot of physics. I need some help on a problem set involving calculating moments

    instructions: calculate the moment produced by the force F in each case about the axis of rotation.

    i have attached two examples, hope the drawings are clear enough.

    Thank you for your help!!

  2. jcsd
  3. Feb 4, 2009 #2
    i read the sticky about why no one answers and maybe i needed to show some work to get a response.

    for the first one i am pretty sure you just multiply the 39 N by the 1.2 m for an answer of -46.8 (the instructions state the counter clockwise is negative)
    again im not sure if thats correct though.

    for the other i honestly dont have any idea, not asking for answers just not even sure how to approach it.

  4. Feb 4, 2009 #3
    There's a kind of standard format to use for asking homework questions. People are helpful, but they want to see some attempted work first. Do you know the formula for the moments? If so, do you see which quantities go into it?
  5. Feb 4, 2009 #4
    i am a new guy too... lol, but i think i can solve the problem...
    but do you consider other forces in the problem?
  6. Feb 4, 2009 #5
    i dont believe you need to consider other forces (gravity, normal) or anything like that.
    this is review and its actually driving me nuts i cant remember how lol.
  7. Feb 4, 2009 #6
    You posted while I was, so I didn't see. Sorry.
    So, does that 39N force tend to cause a CW or CCW rotation?
    Look under your keyboard. You seem to have dropped some units of measure.:wink:
    In the second part, what do you know about calculating the effective force when there is an angle given?
  8. Feb 4, 2009 #7
  9. Feb 4, 2009 #8
    ya i figured our posts overlapped.
    i know the it will be a clockwise rotation, but is it really just as simple as multiplying the force and distance?

    the angle one i assume i make it into a right triangle and use sin51 = x/275lbs to find the vertical component?
  10. Feb 4, 2009 #9
    well i was getting help and then everyone vanished?
    was i on the right track?
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook