دانلود رایگان کتاب Simple Machines – Terri Wakild
Since the beginning of time, humans have searched for ways to make their work easier. Simple machines are the most basic of the machines that we use daily to make work easier. Simple machines have been around for thousands of years, and have accomplished such great things as the building of pyramids, the creation of Stonehenge, and other fantastic man-made architectural creations through time.
Machines, from simple to very complex, surround us as we go through our day. We use them as we go about our daily routines, to clean, move, create, repair, relax, have fun, and accomplish work. In this unit students will learn what the six simple machines are, how each of them can make work easier, and where we use them every day in our own lives.
A machine is a device that allows people to do work with less effort. Simple machines have few or no moving parts to them. These machines help us to move objects closer, apart, or to raise them to different levels by increasing the force or changing the direction of the force. Simple machines offer a mechanical advantage; however, the same amount of work is needed to perform the same job. The simple machine lessens the effort needed to do the same amount of work, making it appear to be easier. The consequence is that we may have to exert the lesser force over a greater distance.