Understanding the Physics Behind Moving a Car with a Rope and a Pole

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Homework Help Overview

The problem involves understanding the mechanics of moving a car using a rope attached to a pole while on a downhill incline. The original poster seeks to understand why pulling or pushing perpendicularly on the rope makes it easier to move the car compared to pushing it directly.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning

Approaches and Questions Raised

  • The original poster attempts to relate the tension in the rope to the force required to move the car, questioning the relationship between the applied force and the force needed to push the car. Some participants suggest considering the angle of the rope and its effect on the force exerted on the car.

Discussion Status

Participants are actively engaging with the problem, exploring different interpretations of the forces involved. There is a hint provided regarding the components of the applied force, indicating a productive direction in the discussion.

Contextual Notes

The original poster expresses uncertainty about their understanding of trigonometric relationships in this context, which may affect their reasoning about the forces at play.

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Homework Statement


You attach a strong rope or steel cable to a light pole and a car parked on a downhill incline. If you have a student lift, pull, or push perpendicularly on the rope in the center it will be easier to move the car than if you were to push it. Why? Prove this mathematically.


Homework Equations





The Attempt at a Solution


I know it has something to do with the tension, but I can't figure out exactly how it works.
 
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Tearsandrille said:
You attach a strong rope or steel cable to a light pole and a car parked on a downhill incline. If you have a student lift, pull, or push perpendicularly on the rope in the center it will be easier to move the car than if you were to push it. Why? Prove this mathematically.

Hi Tearsandrille! :smile:

(do you mean a lamp post? :wink:)

Hint: Suppose the rope has length L, and is at an angle θ to the direct line between the car and the lamp post … if you push it with force F in the middle, what is the force on the car?
 
I did mean lamp post. You'll have to excuse me there, my brain was friend trying to draw all the FBD and vectors.

So, wouldn't the force on the car be tan(theta) * Fapp.

My trig isn't so great, but how is that less than the force you would need to push the car? I believe in order to push the car it would be m*g*sin(theta).
 
Hi Tearsandrille! :wink:

(just got up :zzz: …)
Tearsandrille said:
So, wouldn't the force on the car be tan(theta) * Fapp.

Nope.

Take components along the line of the Fapp. :smile:
 

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