Machines:

Objectives:

    1.    Classify machines.

    2.    Define mechanical advantage and efficiency.

    3.    Calculate the mechanical advantage and efficiency of machines.

Resources:

    http://pc65.frontier.osrhe.edu/hs/science/pwork.htm

Notes:

Machines:

A machine is a device that makes work easier.  A hammer, bicycle ramp,  and scissors are all examples of simple machines

There are always 2 forces involved in machines.

 Since there are 2 types of forces, there are 2 types of work.

Although machines can make work easier, they do not multiply work.

            WI = WO or FE * dE = FR * dR

 The work output can never be greater than the work input.

 Mechanical Advantage:

Mechanical advantage is equal to the number of times a machine multiplies the effort force.

If the MA is > 1, the machine multiplies force.

If the MA is = 1, the machine changes the direction of the force.

If the MA is < 1, the machine increases the distance or speed of an object.

 

Efficiency:

 Efficiency is the comparison of work output to work input.

What is the major reason that the work output would be less than the work input?

                                                                  Friction:

                    The less friction a machine has, the higher its efficiency and work output.