Non-uniform circular motion question

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Homework Help Overview

The problem involves an object suspended from the ceiling of an accelerating truck, requiring the determination of the angle θ that the string makes with the vertical and the tension T in the string. The context is related to non-uniform circular motion, as indicated by the chapter reference in the textbook.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • The original poster attempts to apply equations involving gravitational force and tension but questions the validity of their approach after receiving feedback. Participants discuss the relationship between tension and gravitational force, and the implications of acceleration on these forces.

Discussion Status

Participants are actively engaging with the problem, questioning the assumptions made about the forces involved. Some guidance has been offered regarding the need to reconsider the relationship between tension and gravitational force, and the importance of drawing a diagram to visualize the forces at play.

Contextual Notes

There is a mention of a potential misunderstanding regarding the role of acceleration in the forces acting on the mass, and the discussion hints at the need for clarity on how these forces interact in the context of circular motion.

neshepard
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Homework Statement


An object of mass m=.500kg is suspended from the ceiling of an accelerating truck. Taking a=3.00m/s^2 find the angle θ that the string makes with the vertical and the tension T in the string.


Homework Equations





The Attempt at a Solution


mgsinθ=ma => sinθ=1.5/4.9 =>θ=17.8

mgcosθ=T => T=4.67N

But alas this is incorrect. Where did I fail?
 
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Be careful with mg & T.

For example, in your second equation, you're implying that mg is bigger than T, think about why that can't be true.

Your resolving is fine though, just think about the mg & T, if you need more help just ask.

Edit: I'm also not sure what this has to do with circular motion.
 
As to why circular motion...got me. It's in that chapter in the book.

With T and mg, wouldn't mg be bigger since due to acceleration? If I reverse my equation and have T bigger, is it mg-Tcosθ? and why?
 
The reverse is correct. Draw yourself a diagram and label all of the forces.

The string has to both support the weight of the mass (mg) in the upward direction, but it also acts against the acceleration of the lorry which pushes the mass towards the back of the lorry. Because the net force on it is 0, right? Anyway, I think the diagram should help.
 

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