A great physical science education tool isn’t just exciting while you’re using it; it continues to provoke thought and make real-world connections well after you’ve placed it back on the shelf. Case in point: I recently spent time exploring Pitsco’s T-Bot® Hydraulic Arm. It was a fun challenge using the hydraulic robot arm to pick up and move blocks, and I thought about links to automation and heavy machinery as I used it. But, to my surprise, after I put the device away, what I really couldn’t stop thinking about was my own arm.
Pop quiz: What do a claw hammer, a wheelbarrow, and a broom all have in common? We can skip the suspenseful drum roll here because the title kind of gives it away, but each of these tools is a simple machine called a lever.
After you learn to identify levers, you’ll begin to see that they’re everywhere, all around you. Doors are levers. Fishing rods are levers. Tweezers are levers. And, yes, even your own arm is a lever.
Levers, like the other five simple machines, are arrangements that produce mechanical advantage. That’s to say, in one way or another, they make work easier by multiplying or changing a force applied to it. As we shall see, however, this always, always, always comes at a cost. You can’t get something for nothing.
The most recognizable type of lever is a seesaw. The fulcrum is in the middle. Effort is applied on one side of the fulcrum, which moves a load on the other side of the fulcrum.
By the way, a seesaw is a Class 1 lever. The fulcrum is between the effort and the load. A claw hammer is also acting as a Class 1 lever when pulling out a nail. The nail is the load, the point where the hammer rocks is the fulcrum, and the effort is applied downward in the direction of the hammer’s face.
In a Class 2 lever, the fulcrum is at the far end, and the load is situated between it and the effort. Because the load will always be closer to the fulcrum than the effort, this will once again provide a mechanical advantage. The classic example of a Class 2 lever is a wheelbarrow.
It creates a mechanical disadvantage. However, the tradeoff can still be useful. The payoff for the additional force required is that the load (rather than the effort) moves a greater distance. A broom is a Class 3 lever.
Now we have the information we need to jump into our T-Bot challenge.
Identify every lever on the T-Bot. For each, determine where exactly the fulcrum is located, where the effort is being applied, and where the load is to be found. With this information, categorize the levers you find as one of the three types.
You’ll need to operate the T-Bot to see where each plunger applies its force and where it causes the bot to pivot. This activity makes for a great discussion because multiple people may develop alternate theories.
The answers are below, but don’t peek until you’ve tried it out and formulated your own ideas.
There are three relatively straightforward levers on the T-Bot and one additional lever, which we will discuss last.
OK, nitpickers, we’ve labeled this as one lever, but it’s really two parallel and identical levers operating off of the same input force. Two levers for the price of one! Yay!
You’ll notice that we have accounted for three of the T-Bot’s four operating plungers. Here’s where it gets a little tricky.
In other words, what we have is a Class 2 lever!
If you’ve made it all the way through this activity, I can almost guarantee that you’ll start seeing levers all around you – and as a part of you. Along those lines, here’s a good bonus question relating to what the T-Bot got me thinking about: what class of lever is your arm? Leave your theory and your reason in the comments!
For more detailed explanations on simple machines and levers, check these out: