Unit Summary # 5

During this unit, we covered the following topics:

1. Work and Power
2. Work and Kinetic Energy
3. Conservation of Energy
4. Simple Machines

Work and Power

The formula for work is

Work= Force * Distance

One thing to remember is that force and distance must be parallel to calculate work.

So, when you carry a box down a hallway, no work is done. When you first lifted the box, work was done.

Another example of work is walking up stairs.

You would multiply your force by the vertical height of the stairs to find the amount of work done.

Work is measured in joules(J).

One think associated with work is power.

The formula for power is

Power= Work / Time

The units for power are Joules/Second but thats a lot to say, so instead we use Watts(W).

Here is the video my group and I made about this topic:

Work and Kinetic Energy

Kinetic energy is the energy of movement

Formulas you need to know for this relationship are

Work= Change in KE

KE=1/2mv² 

Also, since work is equal to the change in KE, you must also know how to find that 

Change in KE= KEfinal - KEinitial

Conservation of Energy/Potential Energy

The Law of Conservation of Energy states that energy can be neither created nor destroyed, only converted.

So, when something is not moving, it has Potential Energy. 

Potential Energy is the energy of position. (height)

As this ball swings, it has varying amounts of potential and kinetic energy.

At the top of its swing, it has only potential energy.

Mid-swing, it has both potential and kinetic. 

The formula you must remember for this is

PE= Mass * Gravity * Height

Simple Machines

Today we have a misconception of how simple machines work. 

We think that simple machines reduce the amount of work you have to do.

This is not true.

Machines reduce the amount of force you use over a longer time. 

The ramp on the truck is a simple machine.

It would take a big force to lift something directly into the truck.

The ramp allows you to use a smaller force over a greater distance.

The work you put in will always equal the work you get out.