What forces are acting on a ball at its highest point ie; Grav force, normal force, etc. Clarification: A ball is tossed up and reaches its highest point, that's the point I need to know what forces are acting upon the ball when its in that stage.

You have a resistor and a capacitor of unknown values. first, you charge the capacitor and discharge it through the resistor. by monitoring the capacitor voltage on an oscilloscope, you see that the voltage decays to half its initial value in 3.00 ms . you then use the resistor and capacitor to make a low-pass filter. what is the crossover frequency fc?