Lever

A lever consists of a bar or plank and a pivot point or fulcrum. Work is performed by the bar, which swings at the pivot point to redirect the force.

Basically, there are three components to a lever, we have force, which we’ll abbreviate as capital F and then we have the fulcrum or pivot point.

Mini-test: LEVER 

Question 1: The pivot of a lever is called a
A.  
B.  
C.  
D.  
Question 2: A wheelbarrow is
A.  
B.  
C.  
D.  

 

Next Lesson: Mechanical Advantage

The transcript is for your convenience.
Now, so we don’t have two Fs, we’re going to abbreviate this as PP and then finally we have weight, which we’ll abbreviate this as capital W. Now, those are the main three components

Now, there’s also a bar and the work is performed by the bar, so the easiest way for me to illustrate this is through the example of a seesaw. We have a seesaw, we have something in the middle it’s balancing on over here, force is applied, which I’m going to abbreviate as F. Here’s the pivot point and then over here is the weight. Now, this right here this board is what we call the bar and so work is performed by the bar, which swings at the pivot point. It swings right here to redirect the force, so the force is pushing down here, but the pivot point allows that force to be applied over here to push the weight up.

Now, there are three different types of lever. There’s first class lever, second class, and third class and so the different types of levers depend on the order of these three components, force, pivot point and weight. A seesaw happens to be a first class lever. The first class lever is when you have the pivot point between the force and the weight. Now, another word for weight is resistance, another word for force is effort, so there are lots different words that can be used here that can be interchangeable.

Some other examples of a first class lever in addition to a seesaw would be something like balances, nail extractors or scissors. Now, with the second class lever, the weight is between the force and pivot point. The easiest way to illustrate these types of levers is through a seesaw, because when we start using examples like nail extractors are a type of first class lever. It’s hard to really imagine what that look like in the placement of force, pivot point and weight. I’m going to rearrange our seesaw here to be a second class lever, so we would have force over here, but we would switch weight and pivot point, so we’d have the weight in the middle and then we’d have the pivot point over here.

Now, that seesaw wouldn’t work really well, I wouldn’t recommend getting on it, so there’s not actually a seesaw that’s an example of the second class lever, instead we have the wheelbarrow. I’m going to do my best to draw a wheelbarrow here, we have the wheel here and then we have the handles. The wheel of course is going to be the pivot point and then we’re going to have the weight and here the load and then over here we’re going to have the force. Because whoever’s pushing the wheelbarrow is going to be picking up over here, so here we have the weight between the force and the pivot point.

That’s an example of a second class lever, as is something like pry bars, bottle openers or nut crackers and then finally we go to the third class lever. Again, if I rearrange my seesaw, we’ll find that the weight is over here, the force is over here and the pivot point is down here. The pivot point stays in the same place, but force and weight switched places. Now, again this the seesaw wouldn’t really work and so I’m going to use a baseball bat as an example of a third class lever. Now, we should never say that a third class lever is when you have weight,  then force, then pivot point. Instead we should say that the force is between the weight and the pivot point, because really you could switch these or then turn this around it would still work exactly the same.

In the same way a second class lever is when weight is between force and pivot point and a first class lever is when pivot point is in the middle. These types of levers are defined by what’s in the middle. Now, we’re going to draw a baseball bat, over here we have weight. Now, really the ball touching the bat is not really weight, but it’s the resistance, so bear with me there and over here we have the force,  because that’s where the hands are and then right here down at the end is where we have the pivot point. Notice that force is in the middle, so it’s a third class lever. Some other examples are fishing rods, hammers and tweezers, so that’s a look at the three types of levers. Now, a lever is one of the six types of simple machines, which uses the concept called mechanical advantage to make work easier.

Next Lesson: Mechanical Advantage