Odpowiedź:
Lever (dźwignia) - one of the simple machines, the task of which is to obtain greater force by applying less force. It is made of a rigid beam suspended on an axle. A lever is part of many mechanisms, which are also often referred to as a lever for short. Depending on the position of the axis in relation to the acting forces, a two-sided and one-sided lever are distinguished. n a two-armed lever, the forces act on the opposite sides of the axis of rotation. The distance from where the force is applied to the axis is called the lever arm.
Wyjaśnienie:
Odpowiedź:
Telephone was invented by Alexander Graham Bell in 1876. First model had to be conected with the other one with a cable. It didn't work very well. Sound quality wasn't good. The outer problem was that when somebody was talking he had to speak into one place. And while listening somebody else he had to use the other part of the machine.