Mechanical Advantage
Mechanical Advantage
Mechanical Advantage (MA) is a calculation that provides a multiplier that allows us to determine the overall advantage that a system provides to us. The calculation for actual mechanical advantage is
$$ \text{MA} = \frac{\text{load}}{\text{effort}} $$
Load is the force that must be overcome by the system to produce movement or do work. Effort is the force applied to the input of a simple machine to overcome the load.
In IPO language, the load is the target output, and the effort is the input.
Advantage and Disadvantage
A mechanical advantage of 1 means that in an ideal system there is no advantage or disadvantage at all. In an actual system, there would be a force disadvantage due to real world factors.
A mechanical advantage greater than 1 means that the system provides a force advantage. This means that the system will require a reduce input force, for a greater output force.
A mechanical advantage less than 1 means that the system provides a speed advantage. This means that the system will require a greater input force, for a reduced output force, but you will receive a speed and distance advantage.
| Mechanical Advantage | Input Force | Output Force | Output Speed | Output Distance |
|---|---|---|---|---|
| 1 | No Change | No Change | No Change | No Change |
| > 1 | Decreased | Increased | Decreased | Decreased |
| < 1 | Increased | Decreased | Increased | Increased |
With simple machines we almost always work with force advantage. With gears, we go between force advantage, and speed advantage.
Every system comes with trade-offs. As Newton's Third Law of Motion states: For every action, there is an equal and opposite reaction. We also know from the Law of Conservation of Energy that energy cannot be created or destroyed, only transformed. This means that we cannot generate a greater force without some form of trade-off.
What is means, realistically, is that if we want a system to give us a large force advantage, we are going to need to move the input a greater distance than the output would move.
Ideal Calculations
Unless otherwise stated, calculations are usually in ideal scenarios, which means they ignore external factors, such as friction, heat loss, internal and external forces within the system, material deformation, etc.
Identifying Mechanical Advantage
Each simple machine has it's own way of calculating ideal mechanical advantage. The calculations are all here, but will be explained in detail in each section.