Simple Machines: Levers, Pulleys, the "Golden Rule" and Efficiency
Tools that do not add energy — they just make a job feel easier.
Big idea: A simple machine is a device that changes the size or the direction of a force. It lets you lift a heavy stone with a small push, or pull down on a rope to raise a bucket up. But it never gives you something for nothing: what you save in force you always pay back in distance.
By the end of this lesson you will be able to:
- say what a simple machine does and name a lever and a pulley;
- use the balance rule of a lever, F1 · l1 = F2 · l2;
- describe the moment of a force and why a longer arm helps;
- tell a fixed pulley from a movable pulley;
- explain the "golden rule" of mechanics;
- work out the efficiency (КПД) of a machine.