2 weights on strings, 1 attached to pulley, the other end anchored

  • #1

Homework Statement


https://imgur.com/jE8SMDR
upload_2018-6-5_12-35-6.png


That's a drawing of the problem. I need to solve for the ? weight.

Homework Equations


not sure

The Attempt at a Solution


none, I don't want the answer, I just want the relevant equations. I haven't taken physics in a few years though (I'm out of college, trying to help a friend in high school physics). I used to be pretty good at this but if you don't use it for a while I guess you forget.
 

Attachments

Last edited by a moderator:

Answers and Replies

  • #2
berkeman
Mentor
59,071
9,168

Homework Statement


https://imgur.com/jE8SMDR That's a drawing of the problem. I need to solve for the ? weight.

Homework Equations


not sure

The Attempt at a Solution


none, I don't want the answer, I just want the relevant equations. I haven't taken physics in a few years though (I'm out of college, trying to help a friend in high school physics). I used to be pretty good at this but if you don't use it for a while I guess you forget.
Welcome to the PF.

Do you remember how to draw free body diagrams (FBDs)? With those, if nothing is moving, then the sum of all vector forces on each object must be zero. Can you show us your FBDs?
 
  • #3
gneill
Mentor
20,913
2,862
Hi wolfpack4417,

Welcome to Physics Forums!

I'm afraid that we can't provide any help without you showing some effort first. You must have some idea of some formulas you'll need, what sort of quantities and principles are involved, how forces sum, and so forth. You should at least be able to draw and label a Free Body Diagram (FBD) for the point where the strings meet.

Edit: Oops! @berkeman beat me to it!
 
  • #4
Oh I do remember Free Body Diagrams, I'm at work right now, but I'll google that when I get home and try to draw some. I'm 27 and I took physics when I was 21, so it's a little blurry. My cousin asked me to try to help her with her homework and I felt like I would be able to remember enough to do it, but when she sent me the problem I had no idea haha.

Also when I was trying to solve it on my own, I felt like the length of the ropes would be relevant but she said she didn't remember the teacher telling her those values. Am I wrong in that assumption? It isn't due for 2 days she said, so she can ask in class tomorrow if she needs the lengths.
 
  • Like
Likes haruspex
  • #5
gneill
Mentor
20,913
2,862
Also when I was trying to solve it on my own, I felt like the length of the ropes would be relevant but she said she didn't remember the teacher telling her those values. Am I wrong in that assumption? It isn't due for 2 days she said, so she can ask in class tomorrow if she needs the lengths.
The rope lengths are irrelevant. Very likely the original problem statement would have declared them to be "light" or "massless", so their lengths would not alter the forces involved, either in magnitude or direction.
 
  • #6
haruspex
Science Advisor
Homework Helper
Insights Author
Gold Member
2020 Award
35,576
6,449
It isn't due for 2 days
Even so, going through an intermediary will slow things down and risks being less helpful to the student. Can you persuade her to come into the thread in person?
 
  • Like
Likes gneill and berkeman

Related Threads on 2 weights on strings, 1 attached to pulley, the other end anchored

Replies
9
Views
1K
Replies
8
Views
6K
Replies
13
Views
6K
  • Last Post
Replies
7
Views
3K
Replies
28
Views
2K
  • Last Post
Replies
3
Views
2K
Replies
4
Views
1K
Replies
4
Views
2K
Replies
42
Views
669
Top