Wind drag problem with a ball hanging on a rope

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Homework Help Overview

The discussion revolves around a physics problem involving a ball hanging from a rope at an angle due to wind drag. The participants are exploring the forces acting on the ball, particularly the tension in the rope and the drag force exerted by the wind.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • Participants discuss the free body diagram (FBD) and express concerns about missing values and the complexity of forces involved. There are attempts to relate tension and drag forces, with some participants questioning the correctness of their approaches and calculations.

Discussion Status

Some participants have offered guidance on simplifying the force diagram, suggesting that the wind force is equivalent to the drag force. There is ongoing exploration of how to accurately represent the forces and their components, with no clear consensus reached yet.

Contextual Notes

Participants are working under the constraints of a homework assignment, which may limit the information available and the methods they can use to solve the problem. There are indications of confusion regarding the relationship between tension and drag forces.

crememars
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Homework Statement
A 1.2 kg ball is hanging from the end of a rope. The rope hangs at an angle of 25 degrees from the vertical when a 15.0m/s horizontal wind is blowing. If the wind’s force on the rope is negligible, what drag force does the wind exert on the ball?
Relevant Equations
the answer is 5.84 N
1665924593232.png

I drew a FBD but I feel like it's wrong because there are too many missing values. I tried this:

Fy = 0
Tcosθ - Fg = 0
Tcosθ = mg
T = (1.2)(9.8) / cos(25)
T = 12.98 N

Fx = ma
Fwind - Tsinθ - Fdrag = ma
Fwind - (12.98)(sin25) - Fdrag = ma

I don't know how to find these missing values. I feel like I'm approaching the situation wrong? I saw one solution solve it like this:

g(tanθ) = a
(9.8)(tan25) = 4.57

Fx = ma
Fx = (1.2)(4.57)
Fx = 5.48 N

but this doesn't make any sense to me.

any help would be appreciated, thank you !
 
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crememars said:
Homework Statement:: A 1.2 kg ball is hanging from the end of a rope. The rope hangs at an angle of 25 degrees from the vertical when a 15.0m/s horizontal wind is blowing. If the wind’s force on the rope is negligible, what drag force does the wind exert on the ball?
Relevant Equations:: the answer is 5.84 N

View attachment 315675
I drew a FBD but I feel like it's wrong because there are too many missing values. I tried this:

Fy = 0
Tcosθ - Fg = 0
Tcosθ = mg
T = (1.2)(9.8) / cos(25)
T = 12.98 N

Fx = ma
Fwind - Tsinθ - Fdrag = ma
Fwind - (12.98)(sin25) - Fdrag = ma

I don't know how to find these missing values. I feel like I'm approaching the situation wrong? I saw one solution solve it like this:

g(tanθ) = a
(9.8)(tan25) = 4.57

Fx = ma
Fx = (1.2)(4.57)
Fx = 5.48 N

but this doesn't make any sense to me.

any help would be appreciated, thank you !
You have too many forces on your diagram. The force from the wind is the force of the drag. So you only have the force from the wind acting to the right.

-Dan
 
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topsquark said:
You have too many forces on your diagram. The force from the wind is the force of the drag. So you only have the force from the wind acting to the right.

-Dan
I think I understood, thank you! so the drag would be equal to the x component of the tension.
 
crememars said:
I think I understood, thank you! so the drag would be equal to the x component of the tension.
Yes.

-Dan
 
topsquark said:
You have too many forces on your diagram. The force from the wind is the force of the drag. So you only have the force from the wind acting to the right.

-Dan
Would that not make it 4.97 N if it is equal to the x-component of the tension in the string?
 
No.
But if you show how you get this value, someone may figure out the error.
 
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It helps to draw your diagram approximately to scale. Then you can tell if the answer you came up with is in the ballpark (sanity check). If you draw the correct arrangement of the 1.3kg force vector on the ball, the drag vector you are solving for, and the 25-degree angle in the right place, that will be everything you need.
 
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