关于

What is a simple machine? In this movie, you'll learn that force is a push or pull that can change the way something moves. A simple machine is a tool that uses force to make work easier. A lever is a bar that rests on a fulcrum, and you can use it to help you left heavy things. A ramp is a simple machine with a slanted surface, and you can use it to help you move things. You'll also learn about other simple machines, such as pulleys and wheel and axles. Find out how everyday tools use simple machines.