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

[Scharles]

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~

 

[tiny-tim]

Hi Scharles!

(have a theta: θ )

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. ​

 

[Scharles]

http://img264.imageshack.us/img264/933/61026765.png

Uploaded with ImageShack.us

does my forces diagram draw wrongly ??

anyway, thanks for answering me~ now i know that R = mg cos theta~~

 

[tiny-tim]

Hi Scharles!

does my forces diagram draw wrongly ??

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

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