How Machines Do Work
What is a machine?
A device that allows you to do
work in a way that is easier.
Ways machines make work easier
1. Increasing the force
Example: A car jack multiplies your force by
having it over a greater distance.
2. Increasing the distance
Example: A ramp allows a person to use less
force to lift a box on to the back of a truck
3. Changing Direction
Example: A weight machine or raising
a flag up a flagpole
Difference between input and
output force?
Input Force – The force you exert on the
machine.
Output Force – The force the machine
exerts on an object.
Example: For a shovel –
input  your force on the shovel
output  the force the shovel
exerts on the dirt
Mechanical Advantage
The number of times a machine increases a
force exerted on it.
Formula: MA= output force
input force
Example: Suppose you exert an input force of 10N on a handheld can opener, and the can opener exerts an output
force of 30 N on a can. What is the mechanical advantage
of the can opener?
M.A. and how machines make work
easier
• Increasing force: M.A. > 1
• Increasing Distance: M.A. < 1
• Changing Direction: M.A. = 1
Ideal vs. Real Machines
For IDEAL machines, the output is always
equal to the input. For REAL machines
(the ones we’re familiar with), the
output is always Less than the input
work because of _________.