"**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<sub>r</sub>*, divided by the effort force, *F<sub>e</sub>*. *IMA* also equals the distance over which the effort is applied, *d<sub>e</sub>*, divided by the distance the load travels, *d<sub>r</sub>*. $$IMA = \frac{\mathbf{F}_r}{\mathbf{F}_e} = \frac{d_e}{d_r}$$"
"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. $$\%\text{ efficiency} = \frac{W_o}{W_i} \times 100$$"
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"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<sub>r</sub>, divided by the effort force, F<sub>e</sub>. IMA also equals the distance over which the effort is applied, d<sub>e</sub>, divided by the distance the load travels, d<sub>r</sub>. $$IMA = \frac{\mathbf{F}_r}{\mathbf{F}_e} = \frac{d_e}{d_r}$$"
"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. $$%\text{ efficiency} = \frac{W_o}{W_i} \times 100$$"
What you'll learn
- 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
Prerequisites
Slides
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