In order to be successfully in applying Newton's second law to a mechanical system,
we must first be able to recognize all the forces acting on the system.
This java applet shows the free-body force diagram for a block sits on an inclined plane.
1. a block sits on an inclined plane:
Click the circle near the right edge and drag the mouse up/down to change the angle of inclination thetaíC
2. Red Arrow represents the gravitational force. ( which has two green force components).
Click near the tip of the red arrow and drag the mouse up/down to change the mass of the block. ( mg)
3. Yellow arrow is the normal force Fn.
Under which conditions the normal force becomes zero (vanish)?
4. Click the up-right corner of the block to apply external force F on that block.
(Drag the mouse to change the vector F, if the mouse is within the circle the force F=0.
5. Click again at the tip of the F vector and drag the mouse button to change the direction of the force F only.
When will we have a maximum net force?
6. The normal force were determined from external force F and the gravitational force mg.
Then we will know the friction between the block and the incline plane.
7. The blue arrow is the friction force. Notice: there is a maximum value.
8. All the force are added together to find the net force NF.(the black arrow)
9. You can change different value of coefficient of static friction from the selection.