s14 (b) Levers
A machine is a device that allows you to do work in a way that is easier or more effective. You may think of machines as complex gadgets with motors, but a machine can be quite simple. For example, think about using a shovel. A shovel makes the work of moving soil easier, so a shovel is a machine.
Levers
Have you ever ridden on a seesaw or pried open a paint can with an opener? If so, then you are already familiar with another simple machine called a lever. A lever is a rigid bar that is free to pivot, or rotate, on a fixed point. The fixed point that a lever pivots around is called the fulcrum.
Levers
How It Works
To understand how levers work, think about using a paint-can opener. The opener rests against the edge of the can, which acts as the fulcrum. The tip of the opener is under the lid of the can. When you push down, you exert an input force on the handle, and the opener pivots on the fulcrum. As a result, the tip of the opener pushes up, thereby exerting an output force on the lid.
Mechanical Advantage
A lever like the paint-can opener helps you in two ways. It increases your input force and it changes the direction of your input force. When you use the paint-can opener, you push the handle a long distance down in order to move the lid a short distance up. However, you are able to apply a smaller force than you would have without the opener.
The ideal mechanical advantage of a lever is determined by dividing the distance from the fulcrum to the input force by the distance from the fulcrum to the output force.
d
Figure 16Mechanical Advantage of a Lever A lever’s input distance and output distance determine its ideal mechanical advantage.
In the case of the paint-can opener, the distance from the fulcrum to the input force is greater than the distance from the fulcrum to the output force. This means that the mechanical advantage is greater than 1.
Different Types of LeversWhen a paint-can opener is used as a lever, the fulcrum is located between the input and output forces. But this is not always the case. As shown in Figure 17, there are three different types of levers. Levers are classified according to the location of the fulcrum relative to the input and output forces.
Have you ever ridden on a seesaw or pried open a paint can with an opener? If so, then you are already familiar with another simple machine called a lever. A lever is a rigid bar that is free to pivot, or rotate, on a fixed point. The fixed point that a lever pivots around is called the fulcrum.
Levers
How It Works
To understand how levers work, think about using a paint-can opener. The opener rests against the edge of the can, which acts as the fulcrum. The tip of the opener is under the lid of the can. When you push down, you exert an input force on the handle, and the opener pivots on the fulcrum. As a result, the tip of the opener pushes up, thereby exerting an output force on the lid.
Mechanical Advantage
A lever like the paint-can opener helps you in two ways. It increases your input force and it changes the direction of your input force. When you use the paint-can opener, you push the handle a long distance down in order to move the lid a short distance up. However, you are able to apply a smaller force than you would have without the opener.
The ideal mechanical advantage of a lever is determined by dividing the distance from the fulcrum to the input force by the distance from the fulcrum to the output force.
d
Figure 16Mechanical Advantage of a Lever A lever’s input distance and output distance determine its ideal mechanical advantage.
In the case of the paint-can opener, the distance from the fulcrum to the input force is greater than the distance from the fulcrum to the output force. This means that the mechanical advantage is greater than 1.
Different Types of LeversWhen a paint-can opener is used as a lever, the fulcrum is located between the input and output forces. But this is not always the case. As shown in Figure 17, there are three different types of levers. Levers are classified according to the location of the fulcrum relative to the input and output forces.
