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We cannot reduce the total work a task needs — but we can make it feel easier by changing the size or direction of the force. That is what simple machines do.
What is a simple machine, and what is mechanical advantage?
- Simple machines make a task easier by changing the magnitude or direction of the force needed (they do not reduce the total work).
- The force we apply is the effort ; the force to be overcome is the load .
- Mechanical advantage is the ratio of load to effort: $$\text{mechanical advantage} = \dfrac{\text{load}}{\text{effort}}$$
Important Definitions
- Simple machine — a device that makes a task easier by changing the magnitude or direction of the force applied, without reducing the total work done.
- Effort and load — the effort is the force we apply to the machine; the load is the force that needs to be overcome.
- Mechanical advantage — the ratio of the load to the effort.
What a simple machine changes
What it cannot change
The magnitude of the force we apply (the effort).
The total work required for the task.
The direction in which we apply the force.
The amount of energy (machines do not create energy).
How easy or convenient the task feels.
The conservation of mechanical energy.
