Lesson Plan

Explain why simple machines make work easier but cannot reduce the amount of work done

Describe the six simple machines and identify everyday examples of each

State and apply the ideal mechanical advantage equation IMA = Fᵣ/Fₑ = dₑ/dᵣ and each machine's specific IMA formula

Define a complex machine and recognize the simple machines that compose one

Calculate the efficiency of a machine using %efficiency = (Wₒ/Wᵢ) × 100

Explain why a real machine's efficiency is always less than 100 percent

9.3

"Simple machines make work easier, but they do not decrease the amount of work you have to do. ... Although it cannot change the amount of work you do, a simple machine can change the amount of force you must apply to an object, and the distance over which you apply the force." "In general, the IMA = the resistance force, F_r, divided by the effort force, F_e. IMA also equals the distance over which the effort is applied, d_e, divided by the distance the load travels, d_r. $$IMA = \frac{\mathbf{F}_r}{\mathbf{F}_e} = \frac{d_e}{d_r}$$" "The efficiency output of a machine is simply the output work divided by the input work, and is usually multiplied by 100 so that it is expressed as a percent. $$%\text{ efficiency} = \frac{W_o}{W_i} \times 100$$"