In the dark in outer space, you observe a glowing ball of known mass 4.0 kg moving in the xy plane at constant speed in a circle of radius 6.5 m, with the center of the circle at the origin (<0, 0, 0> m). You can't see what's making it move in a circle. At time t= 0 the ball is at location <6.5, 0, 0> m and has velocity <0, 65, 0> m/s. Required:
At time t = 0, even though you can't see what's causing the motion, what can you conclude must be the vector Fnet?

Your physics assignment is to figure out a way to use electricity to launch a small 6.0-cm-long plastic drink stirrer. you decide that you'll charge the little plastic rod by rubbing it with fur, then hold it near a long, charged wire, as shown in figure p23.56 . when you let go, the electric force of the wire on the plastic rod will shoot it away. suppose you can uniformly charge the plastic stirrer to 10 nc and that the linear charge density of the long wire is 1.0 x10-7 c/m. what is the net electric force on the plastic stirrer if the end closest to the wire is 2.0 cm away?