Equilibrium is an equality of action, or force, between two or more powers, or weights, acting against each other, by which they destroy each other’s effects, and remain at rest.
The centre of motion is the fixed point about which a body moves.
The axis of motion is the fixed line about which it moves.
The centre of gravity is a certain point on which a body (being freely suspended) will rest, in any position.
The whole momentum or quantity of force of a moving body, is the result of the quantity of matter multiplied by the velocity with which it is moved.
THE MECHANICAL POWERS.
Power is compounded of the weight, or expansive force of a moving body multiplied into its velocity.
The power of a body, which weighs 40 lb., and moves with the velocity of 50 feet in a second, is the same as that of another body which weighs 80 lb., and moves with the velocity of 25 feet in a second: for the products of the respective weights, and velocities are the same.
40 × 50 = 2000; and 80 × 25 = 2000.
Power cannot be increased by mechanical means.