Free-body Force Diagram

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.
 

Usage:

• 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 theta¡C

  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 ¡C

  • 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.