1. Mechanical advantage, Efficiency and WO WI
Simple machines

2. Work output, work input W = Fd
Using a block and tackle, you supply an effort force of 250N and move the rope 3m. The load being lifted is 750N and moves a distance of 1m. What is the work input and work output?
W = Fd; 250N x 3m = 750J
W = Fd; 750N x 1m = 750J

3. Efficiency of a machine
Efficiency = Work Output ÷ work input x 100
Express as a percentage (%)
A force of 1200N is needed to move a box up a ramp. The ramp is 4m long. The ramp raises the 3200N resistance (load) to a height of 1 m. What is the work output, the work input and the efficiency of the ramp?
Work input: W = Fd; 1200N x 4m = 4800J
Work output: W = Fd; 3200N x 1m = 3200J
Efficiency: 3200J ÷ 4800J x 100 = .67 x 100 = 67%

4. Mechanical Advantage for a lever or inclined plane
MA = Resistance force ÷ Effort force
MA = R ÷ E
MA = Effort distance ÷ Resistance distance (length of ramp ÷ height of ramp)
MA = ED ÷ RD
MA = Effort arm ÷ Resistance arm
MA = EA ÷ RA

5. Mechanical advantage for a pulley
Count the number of strands of rope that support the load or resistance force
1 fixed pulley – 1
1 moveable pulley – 2
2 fixed and one moveable pulley – 3
2 fixed and 2 moveable pulleys – 4