an object of mass 5kg in plane on a plane inclined at an angle of 30 degree to the horizontal. calculate the force on the object perpendicular to the plane when the object is at rest.

Answer 1

5g cos30°

think about it. when the plane is horizontal, the angle is zero, and the whole weight is down against the plane (cos 0° = 1)

Answer 2

Why is it that the horizontal is 5gcos30 not 5gsin30