During your lesson on Circular Motion, walk around the room, swinging the ball in a circle above the top of your head, (practice so you don't need to use a lot of wrist motion), as you describe the circular motion and the fact that circular motion requires the application of a constant force directed toward the center of the circle. Get the students to acknowledge that your hand at the center of the circle is causing the ball to travel in a circle. Believe me when I say that, every student will follow you with ~~their eyes ~~their whole body as, you walk around the room, swinging the ball. When you get to the part where you talk about force vectors and circular motion, keep swinging the ball in the circle, and ask every student to tell you, what they think will happen to the ball when you let go. Get an answer from every student. Then let go of the ball. (It would help if you practice with the ball, to you can let go at a predetermined point. You want it to go where you want it to, not through a window or hit a student). Those who guessed (or knew) that it would travel in a straight line will beam. Those who thought it would curve, or shrugged their shoulders with an “I don’t know”, will never forget that it traveled in a straight line. Now would be a good time to go to the white board and draw circles and vector lines with accompanying equations. This is a fun, easy demo. Enjoy!