# Conceptual question

## Homework Statement

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-

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## 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?

TSny
Homework Helper
Gold Member
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?

#### Attachments

• Pull box.png
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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?

TSny
Homework Helper
Gold Member
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?
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?