Remember:
There are 3 kinds of Levers. Every kind of Lever has:
- a balance point (fulcrum)
- a point where the weight is
- a point where force is applied
1. Why is energy needed?
Energy is needed to do work.
2. How do scientists define “work”?
Work occurs when a force moves an object.
3. What is the difference between class 1, class 2, and class 3 levers?
A class-1 lever has the fulcrum located somewhere between the effort and the load. With this kind of lever, the direction of force is changes. Effort applied downward moves the load up. Effort applied upward moves the load down.
A class-2 lever has its fulcrum at one end of a lever arm. The load is between the fulcrum and the effort. With this kind of lever, the direction of effort is not changed. Pushing up on the class-2 lever arm pushes up on the load. Pushing down on the lever arm pushes down on the load. To gain a mechanical advantage, the load is places closer to the fulcrum than to the effort. The class-2 lever always reduces effort.
In a class-3 lever, the fulcrum is at one end, and the effort is applied between the fulcrum and the load. With this kind of lever, the direction of effort is not changed. The load moves in the same direction as the effort. The gain offered by a class-3 lever is one of distance.
4. Explain why a simple machine makes work easier to do but does not save energy.Most simple machines do not save energy. They distribute the force needed to do work over a longer distance.
Generally, simple machines can help us in two ways. We can apply less effort over a greater distance, or we can apply more effort over a shorter distance. Simple machines provide a gain in effort or a gain in distance. In addition, some simple machines change the direction of effort.
5. How does a lever or pulley give you mechanical advantage?Sometimes we may want to lift, push, or pull an objects, or we may need to break or cut them. Some of these jobs require a lot of force. When we use simple machines, we gain a mechanical advantage by increasing the amount of force we can bring to bear on an object.
6. What is friction? When is it necessary to reduce friction?Friction is a force that slows down or stops motion. There is friction when two parts of a machine rub against each other.
One way to reduce friction is by covering surfaces that rub together with grease or oil. Another way is by using wheels.
7. What is the difference between a fixed and a movable pulley?A fixed pulley can change the direction of your force. You pull down on one end of the rope. The load is pulled up by the other end. It takes the same force to lift a load with a fixed pulley as it does without a fixed pulley.
A movable pulley does not change the direction of your force. Like a lever, a movable pulley lets you use less force to lift a load. But you must pull the rope a longer distance than the load moves. The smaller force needed to lift a load with a movable pulley is used over a longer distance. So a movable pulley does not save energy.
8. Where in real life can you find levers and pulleys?
- Examples of class-1 levers are: a seesaw, claw hammer, crowbar, scissors, pliers, and tin snips.
- Examples of class-2 levers are: a wheelbarrow, paper cutter, door, nutcracker, garlic press, bellows, and a bottle opener.
- Examples of class-3 levers are: a fishing pole, hammer, baseball bat, hockey stick, golf club, tennis racket, shovel, pitchfork, hoe, broom, tweezers, ice tongs, and your arms and legs.
- Pulleys are used to lift items from one level to another.
- Pulleys can be fixed or movable or combinations of both.
- Pulleys are used in block and tackles, large cranes, chain hoists, and hydraulic systems.
9. TYPES OF LEVERS:
Levers are simple machines that have a rigid arm around a fixed point or fulcrum.
Force is transferred from one part of the arm to another.
- The input (effort) force is multiplied or redirected into anoutput (resistance) force.
- Levers are divided into three different classes.
- A first-class lever has the fulcrum between the input and output forces.
 A Type 1 Lever. |
Examples of common tools (and other items) that use a
A SECOND-CLASS LEVER has the output force between the fulcrum and the input force.
In a Type 2 Lever, the load is between the pivot (fulcrum) and the effort.
The third-class lever has the input force between the fulcrum and the output force.
In a Type 3 Lever, the effort is between the pivot (fulcrum) and the load.
Type 1 lever include:
| Item | Number of Class 1 Levers Used | |
|---|---|---|
| see-saw |  | a single class 1 lever |
| hammer's claws |  | a single class 1 lever |
| scissors |  | 2 class 1 levers |
| pliers |  | 2 class 1 levers |
A SECOND-CLASS LEVER has the output force between the fulcrum and the input force.
 A Type 2 Lever. |
Examples of common tools that use a type 2 lever include:
| Item | Number of Class 2 Levers Used | |
|---|---|---|
| stapler |  | a single class 2 lever |
| bottle opener | a single class 2 lever | |
| wheelbarrow |  | a single class 2 lever |
| nail clippers | Two class 2 levers | |
| nut cracker | Two class 2 levers | |
 A Type 3 Lever. |
Examples of common tools that use a type 3 lever include:
| Item | Number of Class 3 Levers Used | |
|---|---|---|
| fishing rod |  | a single class 3 lever |
| tweezers | Two class 3 levers | |
| tongs |  | Two class 3 levers |
Different types of LEVERS into their appropriate classes.
