A mass of 11 kg is placed on a frictionless incline which is inclined at an angle of 69 degrees above the horizontal. It is held in place by a rope which is attached to a wall at the top of the incline. The rope is angled 13 degrees above the direction parallel to the incline, however. What is the normal force on the mass in Newtons?

Question

A mass of 11 kg is placed on a frictionless incline which is inclined at an angle of 69 degrees above the horizontal. It is held in place by a rope which is attached to a wall at the top of the incline. The rope is angled 13 degrees above the direction parallel to the incline, however. What is the normal force on the mass in Newtons? 
help me solve please!!!!

MathMate · Answer

First draw a diagram of the system (right), then draw the free body diagram (left), see:

http://imageshack.us/photo/my-images/192/1317926143.jpg/

With the forces isolated, weight (mg), tension on the rope (T), and the normal reaction (N), and the angles (in degrees) known, they can be readily resolved into the x and y-components and N calculated.

The equations to resolve forces are:
Vertical (solve for T)
mg=Tcos(8)

Horizontal (solve for N)
Ncos(21)=Tsin(8)