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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 are the simple machines we study?
Simple machines
Three basic kinds
1. Pulley
Changes force direction
Example:
Raising a flag
2. Inclined plane
A gentle ramp
Example:
A loading ramp
3. Lever
Turns about a pivot
Example:
A seesaw
What is a simple machine?
Simple Machine
Simple
no complicated parts — a pulley, a ramp, a lever
Machine
a device that makes a task easier
↓
A
simple machine
changes the
size or the direction
of the force we apply. It does
not
reduce the total work — only the effort.
- 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 .
What is mechanical advantage?
Mechanical Advantage
Mechanical
to do with the forces in the machine
Advantage
how much the machine gains you
↓
Mechanical advantage
= load ÷ effort (7.12). MA > 1 means the machine lets a small effort move a big load.
- Mechanical advantage is the ratio of load to effort: mechanical advantage = load 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.
