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II. Mechanical Advantage and Efficiency A. Machine- a device with which you can do work in a way that is easier and more effective. 1. Makes work easier by... i. changing the amount of force you exert ii. distance over which you exert your force iii. direction in which you exert your force 2. Input force- force you exert on the machine i. Effort force 3. Output force- force exerted by the machine i. Resistance force B. Multiplying force - if a machine allows you to use less force to do some amount of work, you must apply the input force over a greater distance. 1. Do as much work, but easier 2. Exert smaller force over longer distance. i. Ramp C. Multiplying distance - this machine allows you to exert your input force over a shorter distance than you would without the machine 1. The output force is less than input force 2. Mechanical advantage is less than 1 i. Hockey stuff ii. Bike in high gear D. Changing Direction 1. Raising a sail with a rope 2. If only the direction changes, the input force will be the same as the output force 3. Mechanical advantage will be 1 E. Mechanical advantage is output force divided by input force 1. The number of times a force is exerted on a machine is multiplied by the machine F. Efficiency of Machines 1. Ideal - the input work = output work 2. Reality - output is less than input due to friction i. Less friction - closer to ideal 3. Efficiency compares output work to the input work 4. Efficiency = output work/ input work x 100%

i. Expressed as a percent ii. Higher % - more efficient iii. Ideal machine = 100% 4. Efficient = output work / input work G. Actual and Ideal Mechanical Advantage 1. Actual mechanical advantage - mechanical advantage that a machine provides in a real situation i. Measure true input and output 2. Ideal mechanical advantage - mechanical advantage of a machine without friction i. more efficient a machine is, closer to actual mechanical advantage is to ideal mechanical advantage. =Quiz= = = =1. True= =2. False- increasing= =3. True= =4.False- without= =5. Mechanical Advantage= =6. Input Force= =7. Machine= =8. Ideal Mechanical Advantage= =9. Actual Mechanical Advantage= =10. Efficiency= =11. Output Force= Study Guide 2. Change the amount of work 3. 100% 14. It multiplies distance 17. True 18. True 22. Input 23. distance 24. efficiency 25. 100 26. 70%