Mechanical Advantage

How much does an inclined plane, screw, wedge, pulley

or lever really help you?

• Designers of physical systems know from experience that there are many ways to perform the same task

• There job is to find the MOST efficient

• They are looking to find the tool that converts a small input into a much larger output.

•Mechanical Advantage (MA): the ratio of output force to input force of a given machine

• MA has NO units – it is just a comparison/ratio

• When input and output forces are the same, the MA is 1.

• When a machine has an MA GREATER than 1, this generally means it will make tasks easier and faster to accomplish.

• Question: is it possible to have a mechanical advantage LESS than one???

• Is there ever a time when the input force is GREATER than the output force….and we designed it that way?!

Our fist look at scientific formulas!

• Levers:MA = effort arm length

load arm length

• Pulleys:MA = input distance output distance

Let’s try one together…

1. A wheelbarrow has an effort arm 120 cm long and a load arm 40 cm long. What is the mechanical advantage?

Check your learning!1. Find the mechanical advantage of a

wheelbarrow with an effort arm that is 1.8 m long and a load arm that is 0.50 m long.

2. To lift a load 5 cm with a pulley system, 15 cm of string has to be pulled. What is the MA?

3. What is the mechanical advantage of a pulley system if 4 m of string had to be pulled to lift a load a height of 1 m?