Here are some examples:
* Lever: A rigid bar that pivots on a fixed point called a fulcrum. Examples include crowbars, seesaws, and bottle openers.
* Pulley: A wheel with a groove that allows a rope or cable to run over it. Pulleys can change the direction of force and reduce the amount of force needed to lift an object.
* Inclined plane: A flat surface that is raised at an angle. Examples include ramps and stairs.
* Wedge: A triangular tool that is used to split or separate objects. Examples include axes and chisels.
* Screw: A spiral-shaped rod that can be used to fasten objects or to raise or lower objects.
* Wheel and axle: A wheel attached to a central rod called an axle. This system allows objects to be moved with less force.
Simple machines work by trading force for distance - you may need to move the object over a longer distance, but you will need to apply less force.
For example, imagine trying to lift a heavy rock. You could try to lift it directly, which would require a lot of force. Alternatively, you could use a ramp (inclined plane) to push the rock up. You would need to push it over a longer distance, but the force required would be much less.
