# Normal force on an inclined plane

1. Sep 25, 2006

### mbrmbrg

A crate of mass m = 100 kg is pushed at constant speed up the frictionless ramp (theta= 27.0°) by a horizontal force F.
What is the magnitude of the force exerted by the ramp on the crate?

My x-y coordinate system has x+ pointing up the ramp.

I assume that the force in question is the Normal force, which points directly along my positive y-axis.

No acceleration in the y direction (or x direction either, but that's irrelevent for this part of the problem), so
$\Sigma\\F_{y}=N-mg_{y}=N-mg\cos\theta=0$
which gives $N=mg\cos\theta=(100kg)(9.81m/s^2)(cos27^o)=874N$

But that's not the right answer... (and I don't know what the right answer is, either)

Help?

2. Sep 25, 2006