Lesson 27: Force and Energy
A force can transfer energy when it acts through a distance. Simple machines and falling water connect mechanical work with energy conservation and the energy transferred to the surroundings.
Key Ideas
- A push or pull can transfer energy when it moves something. Simple machines change how we use a force, but do not create energy.
- Gravity pulls water downhill. Moving water can turn a waterwheel or help generate electricity.
- Sunlight helps power winds and the water cycle. This connects wind power and many rivers to the Sun’s energy.
- Magnets can push or pull without touching. They are useful in machines, but they cannot create energy from nothing.
- Energy can spread into the surroundings as heat or sound. It has not vanished, even when less is available for the job we want to do.
Vocabulary
- Force: A push or pull on an object.
- Work: Energy transferred when a push or pull moves something.
- Simple Machine: A device, such as a lever or pulley, that changes the size or direction of a force.
- Friction: A force that resists surfaces sliding past one another.
Discussion Questions
- How do simple machines make a job easier without creating extra energy? What are they actually changing?
- Why does a ramp make it easier to move something heavy upward? What do you give up in exchange for using less force?
- How can a lever help you move something that is much heavier than you are? Where does the extra force come from?
- A ball rolling across the floor eventually stops because of friction. Where did its kinetic energy go?
- How can a hydroelectric dam use gravity to produce useful energy? Where did the water's energy come from in the first place?
Phet Simulation Recommendation:
https://phet.colorado.edu/en/simulations/forces-and-motion-basics