Motion question (2 Viewers)

[ngai]

normal force is the force acting on the object by the ground, not necessarily the net force acting against the object's weight
vertically:
acting upwards, F = Tsin30 + N
acting downwards, F = mg = 100 (g=10)
since object is pulled along horizontal, Fup = Fdown, so N = 100 - 50sin30 = 75

 

[CrashOveride]

thanks, makes sense

when we have weights suspended from strings at different angles, is the normal reaction force always null? coz i just went back at a few of these types of problems and even in worked examples the normal force is not even mentioned and after a quick calculation it turns up the the verticaly compoennts of the tension in hte strings always end up being equal to the weight force so effectively cancelling any normal force? this has come up in all the q's i did on strings and masses but is this a universal thing?

 

[Xayma]

Yes the tension in a string will result in the object not placing a force on the surface hence the surface wont react with a normal. Due to the principle of transmissibility of forces it doesnt matter whether the string is providing the resisting force or a surface.