- #1
zeralda21
- 119
- 1
Homework Statement
I am having trouble understanding the direction of a friction force in a sample problem from Engineering Mechanics, Meriam & Kraige. I will attach a picture for no confusion.
http://i.imgur.com/0EdCofi.jpg
The Attempt at a Solution
Consider only the top free-body diagram. Why is the friction force in that direction?
"The friction forces are assigned in the directions to oppose the relative motion which would occur if no friction were present." So where would the object move if there was no friction? Well, it would not since it is attached to a wire. If not attached, it would(or tendency) to move downward and therefore an frictional force in the opposite direction drawn. So, from my own conclusion I would have chosen:
1) Upward force or 2) No friction force at all since it would not move if there was no friction.
Why am I wrong?