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10.2 Notes. Machines. Example Problem 1. A stage hand uses a pulley system to close the 5500 N curtains a distance of 2 m. She uses 225 N of force as she pulls in 55 m of rope. A. What is the mechanical advantage of using this pulley system? B. What is the ideal mechanical advantage?
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10.2 Notes Machines
Example Problem 1 • A stage hand uses a pulley system to close the 5500 N curtains a distance of 2 m. She uses 225 N of force as she pulls in 55 m of rope. • A. What is the mechanical advantage of using this pulley system? • B. What is the ideal mechanical advantage? • C. Determine the efficiency of the system.
Problem solving steps: • Determine what Fr, Fe, dr, and de are. • Find the right formula • Plug in numbers • Check your answers – does it make sense?
For MA • Fr = • Fe = • de = • dr =
Fr = 5500 N • Fe = 225 N • Divide Fr by Fe and you’ll get 24.4 • This pulley system makes your job 24.4 times easier
For IMA • de = 55 m • dr = 2 m • Divide de by dr and you get 27.5 • In a perfect world – no friction or wasted energy, this pulley system makes your job 27.5 times easier
For efficiency, • Since we have solved for MA and IMA, use the efficiency formula MA/IMA x 100 • 24.4/27.5 x 100 = 88.7% efficient
Do your answers make sense? • MA should be greater than 1. Is it? • IMA should be great than both 1 and the MA. Is it? • Efficiency should be less than 100%. Is it?