Confuse about mg cos@ = R or R cos@ = mg

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Homework Help Overview

The discussion revolves around the forces acting on a body placed on an inclined plane, specifically focusing on the relationship between the gravitational force and the normal reaction force at equilibrium.

Discussion Character

  • Conceptual clarification, Problem interpretation

Approaches and Questions Raised

  • Participants explore the balance of forces acting on the inclined plane, questioning whether the normal force (R) balances the component of gravitational force (mg cosθ) or if the relationship is reversed. There is also a focus on ensuring that the forces perpendicular to the surface sum to zero.

Discussion Status

Some participants have provided insights regarding the equilibrium of forces, suggesting that the normal force balances the gravitational component. However, there is still some confusion about the correct interpretation of the forces involved, and multiple perspectives are being explored.

Contextual Notes

Participants are discussing the setup of the problem, including the angle of the incline and the implications of equilibrium conditions. There is mention of a forces diagram, which may influence the understanding of the problem.

Scharles
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i am quite confusing about those reaction force...
let say a body is placed on inclined plane with angle @...
at equilibrium, what are the forces that balances each other ??

mg cos@ balanced by R or R cos@ balance mg ??

thanks~
 
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Hi Scharles! :smile:

(have a theta: θ :wink:)

I always work it out each time …

you know there can be no acceleration perpendicular to the surface …

so the forces perpendicular to the surface must add to zero …

so R balances mgcosθ. :smile:
 
Hi Scharles! :smile:
Scharles said:
does my forces diagram draw wrongly ??

No, your diagram looks fine (and very cheerful! :biggrin:).

(btw, it's "is my forces diagram drawn wrongly", or "have I drawn my forces diagram wrongly" or "does my forces diagram look wrong" :wink:)
 

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