## 6.1 - Simple Machines Overview

Now that we understand the concepts of work and energy we can discuss how to manipulate them to our advantage. Keep in mind that the amount of work required to do something remains the same no matter how it is done.

There are many ways that a person could go from the basement level of a building to the third floor. She could climb a ladder straight up. She could use a steep set of stairs. She could use a long ramp. She could be carried up by another person. She could take an elevator or an escalator or even a helicopter! No matter how she gets to the third floor, one thing remains the same. Her potential energy has increased. Her PE is only dependent on her height and her mass- it is not dependent on how she got up there. This means that the work required is not dependent on how she got there, too.

Since the work required is the same to go up either way, the distances must be different. The path that requires the greatest force also goes the shortest distance. The path with the smallest force has to travel the greatest distance.

Since force can essentially be traded for distance, simple machines can be built. By definition,

There are many ways that a person could go from the basement level of a building to the third floor. She could climb a ladder straight up. She could use a steep set of stairs. She could use a long ramp. She could be carried up by another person. She could take an elevator or an escalator or even a helicopter! No matter how she gets to the third floor, one thing remains the same. Her potential energy has increased. Her PE is only dependent on her height and her mass- it is not dependent on how she got up there. This means that the work required is not dependent on how she got there, too.

**Work never changes!**This means that no matter how a job gets done, the amount of work required to do that job is constant. Picture yourself riding your bike up a steep hill. If you go straight up you have to pedal very hard- you have to exert a big force. If you keep riding across the hill and zigzag your way up you don’t have to pedal as hard- you have to exert a smaller force.Since the work required is the same to go up either way, the distances must be different. The path that requires the greatest force also goes the shortest distance. The path with the smallest force has to travel the greatest distance.

Since force can essentially be traded for distance, simple machines can be built. By definition,

**a simple machine changes the direction and/or magnitude of a force**. It does not change the amount of work that is done.When applying labels to the forces and distances it is best to keep things together that have to do with the task and with what you have to do. Any work that you do with a machine- the force that you apply, the distance that you travel, is called effort. Any work that would have to be done no matter if a simple machine is being used- the weight of the object, the height it has to lifted to, is called the load.

The equation that one uses with ALL simple machine problems is:

The equation that one uses with ALL simple machine problems is:

Another way to look at this equation is in terms of comparing the forces and the distances to each other. This comparison is called the

**mechanical advantage**. It tells you have many times greater your effort distance is going to be. It also tells you have many times smaller your effort force is.## 6.1 Review Questions

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