In the applet below, mass M1 is resting on the surface of an inclined plane. The mass is being held motionless. The coefficient of kinetic friction, mk, and the coefficient of static friction, ms, can be set with the slide bar. Note that the value of ms is always larger than mk. The hanging mass M2 is connected with a massless string threaded over a frictionless pulley.
When you click "Begin", the system is released (the hand disappears). The masses will move if the net force is greater than the maximum force of static friction. You can adjust the angle of the plane as well as the magnitude of the masses of M1 and M2. The force vectors are drawn to scale. Note that the tension force vectors change when the masses begin to move.
The forces shown are: