Force Diagram Practice
In solving physics problems with Newton's 2nd law, it is often more convenient to break a contact force into components parallel and perpendicular to the contact surface (the frictional and normal components, respectively).
For the following problems, draw the force diagram for the subject of interest. Use normal and frictional components where appropriate. The Red Dot is an indication of the sum of the forces (net force) that you have drawn at any given time; the direction of the net force is given in red in the upper left corner of the applet. Briefly, from reading the problem you will need to determine whether the net force should be zero or not. Then change the direction and/or magnitude of one or more of the force vectors to put the dot at the center (for zero net force) or in the correct direction (for non-zero net force).