Why do tennis balls feel heavy?
The most common is it is damp or humid conditions, like in the south in the United States. the courts that they play on are usually Clay, those courts grab little pieces of clay and get in bedded into the ball, the dampness and the weight of the clay make the ball feel very heavy. the ball tends to land short and requires more power to Land it deep. The conditions , weather, water, type of court, all play a part in why the ball feels heavy.