What makes levers work

So F2 must have this value to balance the force F1 acting down on the right hand side. Since the lever is balanced, we can think of there being an equivalent force equal to F2 and due to F1 , shown in orange in the diagram below, pushing upwards on the left side of the lever.

This is intuitively correct since we know how a long crowbar can create a lot of force for lifting or prying things, or if you put your fingers between the jaws of a pliers and squeeze, you know all about it!

This force magnifying effect or mechanical advantage of a lever is one of the features that makes it so useful. When the lever is balanced, the force F1 produces an equivalent force of magnitude F2 shown in orange. This balances F2 shown in blue acting downwards. Many of the bones in your body act as third class levers. For instance in your arm, the elbow is the pivot, the biceps muscle creates the effort acting on the forearm and the load is held by a hand.

The small bones in the ear also form a lever system. These bones are the hammer, anvil and stirrup and act as levers to magnify sound coming from the eardrum. The bones in our arms and other part of the body are third class levers. We can summarise the above reasoning into a simple equation known as the law of the lever :. A counterbalance is a weight added to one end of a lever or other pivoting structure so that it becomes balanced the turning moments clockwise and anti-clockwise are equalised.

The weight of the counterbalance and its position relative to the pivot are set so that the lever can stay at any angle without turning. The advantage of a counterbalance is that a lever only has to be displaced and doesn't have to be physically lifted. So for instance a heavy road barrier could be raised by a human if it moves freely on its pivot.

If there was no counterbalance, they would have to push down a lot harder on the barrier to lift the other end. Counterbalances are also used on tower cranes to balance the boom so that the crane doesn't topple over. Swing bridges use counterbalances to balance the weight of the swing section. Sometimes the counterbalancing force is provided by a spring instead of a weight. For instance springs are sometimes used on the deck of a lawn mower so a person doesn't have to lift the deck when adjusting the height.

Also springs might be used on the lid of a home appliance such as a chest freezer to stop the lid falling down when raised. A counterbalance used to balance a lever. These are often seen on road barriers where one end of the lever is much shorter than the other end.

A tower crane. The counterbalance consists of a collection of concrete slabs mounted near the end of the boom. Conquip, public domain image via Pixabay. User:HighContrast, CC 3. Hannah, J. Curley, R. Simple machines. Encyclopaedia Britannica. Content is for informational or entertainment purposes only and does not substitute for personal counsel or professional advice in business, financial, legal, or technical matters.

Answer: A lever is one of the six simple machines. Levers can be used as links to connect the various moving parts of a machine, so, for instance, one part of a machine can move another part by pulling a link that can pivot at an intermediate point. Levers also take form in a variety of hand tools such as scissors, pliers, claw hammers and wheelbarrows.

One of the main features of a lever that makes it useful is that it can have a mechanical advantage. This means that when a force is applied to one point on the lever e. So, for instance, a tool called a bolt cutter has long handles which give it a lot of mechanical advantage. The closer the Load is to the Fulcrum, the easier the load is to lift. Examples include wheelbarrows, staplers, bottle openers, nut cracker, and nail clippers. A great example of a Class Two Lever is a wheelbarrow.

A Class 1 lever has the fulcrum placed between the effort and load. The movement of the load is in the opposite direction of the movement of the effort. This is the most common lever configuration. The effort in a class 1 lever is in one direction, and the load moves in the opposite direction. Well, a first-class lever is a stick where the fulcrum is in between the weight and the energy or force moving the weight your hands, for example.

Principle of the Lever. It has been practically found that when two equal forces acting in opposite directions, i. A lever is a simple machine made of a rigid beam and a fulcrum.

The fulcrum is the point on which the beam pivots. When an effort is applied to one end of the lever, a load is applied at the other end of the lever. This will move a mass upward. A lever usually is used to move or lift objects.

Sometimes it is used to push against objects, but not actually move them. Levers can be used to exert a large force over a small distance at one end by exerting only a small force over a greater distance at the other. English Language Learners Definition of lever : a bar or rod that is used to operate or adjust something on a machine, vehicle, device, etc. Revenue lever You can maximize profit by increasing revenue.

Profit levers for revenue include price of the product or services, price of options and bundled or unbundled services, volume or quantity, value proposition and market perception. The ancient Greek mathematician and early scientist Archimedes is typically attributed with having been the first to uncover the physical principles governing the behavior of the lever, which he expressed in mathematical terms.

The key concepts at work in the lever is that since it is a solid beam, then the total torque into one end of the lever will manifest as an equivalent torque on the other end. Before getting into interpreting this as a general rule, let's look at a specific example. Imagine two masses balanced on a beam across a fulcrum.

In this situation, we see that there are four key quantities that can be measured these are also shown in the picture :.

This basic situation illuminates the relationships of these various quantities. It should be noted that this is an idealized lever, so we're considering a situation where there is absolutely no friction between the beam and the fulcrum, and that there are no other forces that would throw the balance out of equilibrium, like a breeze. This set up is most familiar from the basic scales , used throughout history for weighing objects. If you use known weights on one end of the scale, you can easily tell the weight on the other end of the scale when the lever balances out.

The situation gets much more interesting, of course, when a does not equal b. In that situation, what Archimedes discovered was that there is a precise mathematical relationship — in fact, an equivalence — between the product of the mass and the distance on both sides of the lever:.

Using this formula, we see that if we double the distance on one side of the lever, it takes half as much mass to balance it out, such as:. This example has been based upon the idea of masses sitting on the lever, but the mass could be replaced by anything that exerts a physical force upon the lever, including a human arm pushing on it.

This begins to give us a basic understanding of the potential power of a lever. This is where the term "leverage" gets its common definition, often applied well outside the realm of physics: using a relatively smaller amount of power often in the form of money or influence to gain a disproportionately greater advantage on the outcome.

When using a lever to perform work, we focus not on masses, but on the idea of exerting an input force on the lever called the effort and getting an output force called the load or the resistance. So, for example, when you use a crowbar to pry up a nail, you are exerting an effort force to generate an output resistance force, which is what pulls the nail out. The four components of a lever can be combined together in three basic ways, resulting in three classes of levers:.

Each of these different configurations has different implications for the mechanical advantage provided by the lever. Understanding this involves breaking down the "law of the lever" that was first formally understood by Archimedes.

The basic mathematical principle of the lever is that the distance from the fulcrum can be used to determine how the input and output forces relate to each other. If we take the earlier equation for balancing masses on the lever and generalize it to an input force F i and output force F o , we get an equation which basically says that the torque will be conserved when a lever is used:. This formula allows us to generate a formula for the "mechanical advantage" of a lever, which is the ratio of the input force to the output force:.

The mechanical advantage depends upon the ratio of a to b. For class 1 levers, this could be configured in any way, but class 2 and class 3 levers put constraints on the values of a and b.