Arm weight, moreover, as we have seen can also be correctly applied for tone-production while continuously (but lightly) resting on the keyboard for certain light effects.

Do not imagine that it is by an actual fall or release of the weight that tone is produced, and that the greater the weight the quicker the speed.
That is a total misapprehension, and not true when analyzed using classical mechanics. ^[1] An ounce falls with precisely the same speed as a ton although the impact of a ton is a vastly different from the impact of an ounce.

Weight is needed solely as a basis for the finger and hand exertion applied to the keyboard. True, the height from which a weight falls does influence the speed, for a weight gathers speed as it falls. But this fact cannot be taken advantage of in playing the piano since such free fall^[2] of the arm would preclude our attaining any musical certainty. The reason being, that if you "drop" your arm uncontrolled upon the key, you cannot possibly feel and judge how much force is needed by that key for that particularly desired tone and it always should be a desired tone. Nor can you thus provide the due degree of acceleration needed during key-descent. An uncontrolled drop of the arm would instead reduce everything to mere guesswork and probability. This approach goes against the expression of music-sense. Therefore, never let your arm drop or fall upon the keys uncontrolled by its upholding muscles.

When playing forte by arm-movement, it is an advantage to allow your arm to descend and subside from a small distance. The inertia^[3] of its mass is thus in a measure overcome as a preliminary to the actual tone-producing act which, remember, must never begin until the surface of the keyboard is reached. Therefore, even in this case, you must reach the keys quite gently so that you can still judge the resistance met with from them.

Moreover, realize that weight never really produces the tone. As already insisted upon, weight can form a basis for the activities of the finger and hand. Arm-weight could only be said to "produce" the tone, if allowed to subside with the key unaided by any intervening exertion of the finger and hand, which is manifestly impossible. Therefore, whenever you apply weight never forget to use both hand and finger.

[1] Classical mechanics: Classical mechanics is a physical theory describing the motion of macroscopic objects such as projectiles, spacecraft, planets, fingers, hand and forearm.

[2]free fall: A free falling object is an object that is falling under the sole influence of gravity. Any object that is being acted upon only by the force of gravity is said to be in a state of free fall.

[3]inertia: A property of matter by which it continues in its existing state of rest or uniform motion in a straight line, unless that state is changed by an external force.