Lesson 59: Simple Machines and Work
Simple machines change the size or direction of an applied force. Levers, ramps, pulleys, and wheels connect force and distance with the scientific meaning of work.
Key Ideas
- In science, work happens when a push or pull moves an object. Holding something still can feel tiring without moving the object.
- A simple machine can let us use a smaller force over a longer distance. It does not create extra energy.
- A lever turns around a support called a fulcrum. In our setup, moving that support closer to the load makes lifting easier.
- Simple machines can change the size or direction of a force. A fixed pulley lets us pull down to lift something up.
Vocabulary
- Work: Energy transferred when a push or pull moves something.
- Lever: A stiff bar that turns around a support, like a seesaw.
- Fulcrum: The support a lever turns around.
- Inclined plane: A sloping surface, like a ramp, that lets us lift something gradually over a longer distance.
Discussion Questions
- A wheelchair ramp is much longer than the height it climbs. Why must it be built that long, using today's lesson?
- Scissors have levers and sharp, wedge-shaped blades. Find the point where the blades turn. Is it easier to cut near that point or near the tips? Try it with paper.
- If a simple machine cannot create energy, why use it? Think about force, distance, and the direction of a push or pull.
Supplies
- A sturdy ruler or stick, a small block or eraser, and a heavy book