Physics is ever prevalent in the world of sports. Tennis is no exception to that.
A tennis racquet, much like a baseball bat, has a sweet spot. A tennis racquet however, has 3 so called sweet spots. One is right by the center, and this is a node. A player will feel little to no vibration when the ball is hit in this spot. There is another sweet spot is at the center of percussion. The COM is located shortly below the node. The third spot is located even below that, and it is at this spot where you get the maximum bounce. The force you feel in your hand is due to the vibrations in the racquet so at the node, it makes sense that that is where the sweet spot for most is.
At the top of a racquet is the dead spot. It is at this spot that the ball barely moves. This is because all the energy from the ball is absorbed by the racquet and doesn't go back to the ball. You can feel, hear, and see when this happens.