1. Mechanical Advantage and Efficiency

2. Mechanical Advantage
A machine’s MA is the number of times a force exerted on a machine is multiplied by the machine.
The MA is a ratio between the output and input force
MA = Output Force / Input Force

3. If you exert a force of 20 N on a can opener, and the opener exerts a force of 60 N on the can, the ideal mechanical advantage of the can opener is 6 2
1200 3 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32

4. Mechanical Advantage > 1
A machine with a mechanical advantage of greater than 1 multiplies the input force.
Examples: can opener
a ramp

5. Mechanical Advantage < 1
A machine with a mechanical advantage of less than 1 does not multiply the force but increases the distance and speed.
Example: Hockey Stick
Paper Fan

6. Mechanical Advantage = 1
A machine with a mechanical advantage of 1 means that a machine changes the direction of the force.
Example: Rope

7. The mechanical advantage of a machine that changes only the direction of force is1
Less than 1
Greater than 1 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32

8. Efficiency of Machines
To calculate the efficiency of a machine, divide the output work by the input work and multiply the result by 100 percent.
Efficiency = Output work * 100%
Input work

9. The efficiency of a machine compares
Force to mass
Output work to input work.
Force to friction
Friction to mass 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32

10. Actual Mechanical Advantage
The actual mechanical advantage is the mechanical advantage that a machine provides in a real situation.

11. Ideal Mechanical Advantage
The ideal mechanical advantage is the mechanical advantage of a machine without friction.
The more efficient a machine is, the closer the actual mechanical advantage is to the ideal mechanical advantage.

12. An ideal machine would have an efficiency of
1 percent
10 percent
50 percent
100 percent 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32

13. If tight scissors have an efficiency of 50 percent, how much of your work is wasted overcoming friction?
All of it
None of it
One half of it
10 percent of it 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32

14. Without friction there would be
Less machine efficiency.
Greater output work than input work.
Greater input work than output work.
Equal input and output work. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32