Levers and Load-Effort Systems
Definition
Lever
A rigid bar that pivots on a fulcrum to move a load with an applied effort.
Note
Recap of Key Terms
- Load (L): The object or resistance that needs to be moved.
- Effort (E): The input force applied to move the load.
- Fulcrum: The fixed pivot point of the lever.
- Load Arm: Distance from fulcrum to the load.
- Effort Arm: Distance from fulcrum to where effort is applied.
Formula
To calculate effort or load, use:
$$\text{Effort} × \text{Effort Arm} = \text{Load} × \text{Load Arm}$$
Note
For a lever to be balanced, the clockwise moments must equal the counterclockwise moments.
Rearranged versions:
$$\text{Load} = \frac{\text{Effort} × \text{Effort Arm}}{\text{Load Arm}}$$
$$\text{Effort} = \frac{\text{Load} × \text{Load Arm}}{\text{Effort Arm}}$$
Example question
A lever has a load of 50 N located 2 m from the fulcrum. The effort is applied 4 m from the fulcrum. Calculate the effort.
Solution
$$\text{Effort}=\frac{50×2}{4}=25 \text{ N}$$
