PHYSICS
posted by Mar .
An object of mass M = 1,284 g is pushed at a constant speed up a frictionless inclined surface which forms an angle θ = 50 degrees with the horizontal. What is the magnitude of the force that is exerted by the inclined surface on the object?
(I'm using 1.284*9.81*cos50 to get the force but I'm still getting a wrong answer.)
Can anyone explain the steps into solving this kind of problem.

The normal force depends upon the angle the pushing force is applied to the block. If it is applied parallel to the inclined surface (along the direction of motion), I agree with your equation. Your answer would be in Newtons.
Other force application directions are possible. 
Tilt your axis such that, Y is pointing to the opposite of Weight of M. And X is pointing towards the right. (like usual). [The axis shown in the diagram requires you to find Fnet, which I don't know how to find; thus use this method].
In that case,
Positive being up,
W(of M)+Ncos50=0
=> N=Mg/cos50
plug your numbers, that's your answer.