There are six simple machines that help us do work: wheels and axles, pulleys, levers, wedges, screws, and inclined planes (ramps). Simple machines help us by following the simple rule God made for them: When you increase the distance over which force is applied, you decrease the force needed.
Here are some experiments to try around your house. See if you can figure out what they have in common:
- Try to open a door in your house by pushing (or pulling) the middle of the door rather than the side with the doorknob.
- Try jumping up your stairs two at a time with both feet instead of one at a time.
- Try turning a bike wheel near the axle and then near the rim.
- Try pressing a stapler near the hinge instead of at the stapling end.
What do you notice? In each case, you should have felt that it was harder when you did it “wrong” than when you did it the way you usually do. It should have been harder to open the door from the middle, to press the stapler near the hinge, to jump up two stairs with both feet, and to spin the wheel near the axle. When you use a machine—the hinge, the stairs, the wheel—as you’re meant to, the job becomes easier. If you increase the distance over which you’re applying force, you’ll need less force.
Here are some more examples:
- Try taping a ruler to a faucet handle to make it longer. The tap will be easier to open and close.
- Maybe you’ve seen a delivery person pushing a refrigerator on a wheeled cart up a long ramp into a truck. That’s a lot easier than lifting it the shorter distance from the ground to the truck!
- A wheelbarrow works well because the long handles put the lifter far away from what’s being lifted. The longer the handles are, the easier the load is to lift.
- Why do we screw lids onto jars instead of hammering them on? It’s not just to keep the jar from breaking. It’s because it takes less force.
- It’s much easier on a car’s engine to go up a mountain using curvy switchbacks instead of a straighter but steeper road.
All these simple machines increase the distance of the effort but decrease the force needed. Let’s thank God for this amazing rule God created to make our work easier!