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: Conceptual question

  1. Feb 8, 2015 #1
    1. The problem statement, all variables and given/known data
    3. A bird feeder of large mass is hung from a tree limb.
    A cord attached to the bottom of the feeder has
    been left dangling free. Curiosity gets the best of a child, who
    pulls on the dangling cord in an attempt to see what's in the
    feeder. The dangling cord is cut from the same source as the cord
    attached to the limb. ls the cord between the feeder and the limb
    more likely to snap with a slow continuous pull or a sudden down-
    ward pull? Give your reasoning.

    2. Relevant equations

    3. The attempt at a solution
    I think that likelihood for the cord to snap is the same, because the forces acting on the cord are the same in both ways.

    What do you think?
  2. jcsd
  3. Feb 8, 2015 #2


    User Avatar
    Homework Helper
    Gold Member
    2017 Award

    Consider a simpler situation first. Suppose a heavy box sits on a slippery surface and you pull the box across the surface with a string as shown. To avoid breaking the string, should you pull slowly or snap the string quickly? Why does it make a difference?

    Attached Files:

  4. Feb 8, 2015 #3
    My experience tells me that I would pull the string slowly, but I can't prove why. Maybe it has something to do with static frictional force?
  5. Feb 8, 2015 #4


    User Avatar
    Homework Helper
    Gold Member
    2017 Award

    There is no friction. What if you considered the case where the box on the slippery surface is made of solid lead and the case where the box is made of styrofoam? In which case would it be harder to break the string? Why?
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted