14-3 Mechanical Advantage and Efficiency Answer on a separate sheet of paper Objectives: 1. How does the actual mechanical advantage of a machine compare to its ideal mechanical advantage? 2. Why is the efficiency of a machine always less than 100 percent?

Mechanical Advantage Mechanical advantage of a machine is the number of times that the machine increases an input force. MA = Output force / Input force MA = Input distance / Output distance

MA = ? MA = Id / Od Input Distance = 1.8 m MA = 1.8m / .3m A woman drives her car up onto wheel ramps to perform some repairs. If she drives a distance of 1.8meters along the ramp to raise the car .3meters, what is the mechanical advantage? MA = ? Input Distance = 1.8 m Output Distance = .3m MA = Id / Od MA = 1.8m / .3m MA = 6

If you exert 100 N on a jack to lift a 10,000N car, what would the jack’s MA be? Input Force = 100N Output Force = 10,000N MA = Of / If MA = 10,000N / 100N MA = 100

Efficiency Efficiency is the percentage of the work input that becomes work output. Because there is always some friction, the efficiency of any machine is always less than 100%. Efficiency = (Work output / Work input) x 100

You have just designed a machine that uses 1000 J of work from a motor for every 800J of useful work the machine supplies. What is the efficiency? Efficiency = ? Work Output = 800 J Work Input = 1000J Efficiency = (Wo / Wi) x 100 Efficiency = (800 / 1000) x 100 Efficiency = 80%

Go back to the 14-3 Objectives and answer them again. 1. How does the actual mechanical advantage of a machine compare to its ideal mechanical advantage? 2.Why is the efficiency of a machine always less than 100 percent?