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: Pulley, friction, acceleration

  1. Oct 10, 2012 #1
    1. The problem statement, all variables and given/known data
    http://imageshack.us/a/img703/7864/physicsb.png [Broken]
    From the image above:
    a) If there is no friction between A and surface, what is the blocks' acceleration?
    b) With coefficient of 0.2?
    Last edited by a moderator: May 6, 2017
  2. jcsd
  3. Oct 10, 2012 #2
    What do you think the acceleration would be?
  4. Oct 10, 2012 #3


    User Avatar
    Science Advisor
    Homework Helper

    hi joel! :wink:

    show us what you've tried, and where you're stuck, and then we'll know how to help! :smile:
  5. Oct 10, 2012 #4
    So I found acceleration to be 4.9m/s/s without friction and 3.92m/s/s with a coefficient of kinetic friction of 0.2. Is this correct?
  6. Oct 10, 2012 #5
    4.9 [itex] m/s^2 [/itex] is correct for the acceleration without friction. You could figure that out just by looking at the diagram because you know that if the force of gravity pulling down 1 block pulls down twice that mass, then the system will accelerate at half of the acceleration for one block. In your case, it's half of g.

    For the acceleration of the block including friction, I'm not totally sure, but 3.92 [itex] m/s^2 [/itex] sounds reasonable. You probably got it.
  7. Oct 11, 2012 #6


    User Avatar
    Science Advisor
    Homework Helper

    hi joel! :smile:

    (just got up :zzz:)

    yes, howie8594 :smile: is correct …

    you can pretend everything is in a line …

    force 9.8, mass 2, -> acceleration 4.9​

    similarly for the friction µ = 0.2 …

    force 9.8 * (1 - 0.2), mass 2, -> acceleration 4.9*0.8 :wink:
  8. Oct 11, 2012 #7
    Thanks a lot for your help and confmirations. Highly appreciated :)
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook