• Support PF! Buy your school textbooks, materials and every day products via PF Here!

Hanging bag by a vertical rope

  • Thread starter Toranc3
  • Start date
189
0
1. Homework Statement

A 115kg mail bag hangs by a vertical rope 3.3m long. A postal worker then displaces the bag to a position 2.2m sideways from its original position, always keeping the rope taut.

As the bag is moved to this position, how much work is done by the rope?
2. Homework Equations

W=F*d

3. The Attempt at a Solution
Tx=-Tcos(theta)
Ty=Tsin(theta)

W=-Tcos(theta)*d

T/3.3m =mg/2.5m to get T

I wanted to know why this is zero. Doesn't the Tension have a negative component in the opposite direction of motion, so the work done will be negative. The answer is zero but I just wanted an explanation on this one. Thanks!
1. Homework Statement



2. Homework Equations



3. The Attempt at a Solution
 

lewando

Homework Helper
Gold Member
1,339
133
Wrope = Fropedrope.

If Wrope = 0 and Frope (tension) is nonzero, what must be true about drope?
 
189
0
its zero
 
189
0
ive got it! thanks!!
 

lewando

Homework Helper
Gold Member
1,339
133
Which it is, due to the length of the rope not changing. All clear?
 
189
0
Which it is, due to the length of the rope not changing. All clear?
Wouldn't it also be correct to say that T is perpendicular to the displacement?
 

lewando

Homework Helper
Gold Member
1,339
133
No, it is at some angle, but not 90°.
 

Related Threads for: Hanging bag by a vertical rope

Replies
5
Views
33K
  • Posted
Replies
3
Views
4K
  • Posted
Replies
12
Views
274
Replies
2
Views
5K
Replies
9
Views
6K
  • Posted
Replies
14
Views
5K
  • Posted
Replies
3
Views
11K

Physics Forums Values

We Value Quality
• Topics based on mainstream science
• Proper English grammar and spelling
We Value Civility
• Positive and compassionate attitudes
• Patience while debating
We Value Productivity
• Disciplined to remain on-topic
• Recognition of own weaknesses
• Solo and co-op problem solving
Top