How Do You Calculate the Horizontal Force on a Pendulum?

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Homework Help Overview

The discussion revolves around calculating the horizontal force acting on a pendulum ball that is displaced at an angle from the vertical. The problem involves understanding the forces acting on the pendulum, including tension, gravitational force, and the applied horizontal force.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • Participants discuss the classification of the problem and the forces involved, including tension and gravity. Questions arise about the relationship between the components of tension and how to calculate them without knowing the total tension.

Discussion Status

Participants are actively engaging with the problem, exploring the relationships between the forces and their components. Some guidance has been provided regarding the assumptions about the angles and components of the forces, but there is no explicit consensus on the calculations yet.

Contextual Notes

There is a focus on the geometry of the force diagram and the angles involved, with some participants questioning their assumptions about the orientation of the forces. The discussion reflects uncertainty about how to proceed with the calculations based on the given information.

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Homework Statement



A 2.0 kg pendulum ball is pulled 30° from the vertical by a horizontal force Fpull. What is the magnitude of Fpull?

Homework Equations



F=ma

The Attempt at a Solution



I'm rather lost with this one - I'm not even sure how to classify it. Any help at all - even a point in the right direction - would be greatly appreciated.
 
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Unless the problem says otherwise, assume Fpull is at a 90° angle from the vertical.

Force diagram. You'll have three forces: tension, Fpull, and the force of gravity. The tension will have two components.
 
sorry, misread the post. it said horizontal. So it is definitely a right angle from the vertical
 
Yes -- diagram it.
 
Hi all, thanks for your input. Is it right to assume that the force of gravity = the y component of the tensional force, and that the force applied to the ball = the x component of the tensional force? If so, how can I calculate Tx without knowing the magnitude of T? (If my assumptions are correct, I can calculate Ty using Fg, but I don't know how that value could help me.)
 
nx01 said:
Hi all, thanks for your input. Is it right to assume that the force of gravity = the y component of the tensional force, and that the force applied to the ball = the x component of the tensional force?
Yes.
If so, how can I calculate Tx without knowing the magnitude of T? (If my assumptions are correct, I can calculate Ty using Fg, but I don't know how that value could help me.)
If T is the total tension and the angle is 30o, what in terms of T are Tx and Ty?
 
If the ball is 30o from the vertical to the right, then T is oriented 130o from the positive direction of the x-axis. Then Tx =Tcos130, and Ty=Tsin130?
 
nx01 said:
If the ball is 30o from the vertical to the right, then T is oriented 130o from the positive direction of the x-axis. Then Tx =Tcos130, and Ty=Tsin130?
No, not 130. How did you calculate that?
 
Oops, I meant 120. I've attached a picture (.jpg) showing how I calculated the angle.

Thanks for your responses so far!
 

Attachments

  • Note_20131101_221130_01.jpg
    Note_20131101_221130_01.jpg
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  • #10
nx01 said:
Oops, I meant 120. I've attached a picture (.jpg) showing how I calculated the angle.

Thanks for your responses so far!
Yes, that's better.
 
  • #11
I've got the answer :)

For anyone who might come across this post in the future:

Ty=Fg=mg=2*9.8=19.6=Tsin120
So T=22.63
|Fpull|=|Tx|=|Tcos120|=|-11.3|=11.3
 

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