Which of the following levers would be best to use to move a specific object if your only objective was slight movement of the object? Select one:
a. 1st class with resistance arm of 10 and force arm of 10
b. 2nd class with resistance arm of 10 and force arm of 20
c. 3rd class with resistance arm of 20 and force arm of 10
d. Each would be just as effective as the others
The correct answer and explanation is:
The correct answer is b. 2nd class with resistance arm of 10 and force arm of 20.
Explanation:
In lever mechanics, the effectiveness of a lever in moving an object is determined by the length of the resistance arm (distance from the fulcrum to the load) and the length of the force arm (distance from the fulcrum to the point where the force is applied). The mechanical advantage (MA) of a lever can be calculated using the formula: MA=Force arm lengthResistance arm lengthMA = \frac{\text{Force arm length}}{\text{Resistance arm length}}
When the force arm is longer than the resistance arm, the lever provides a mechanical advantage, which allows a smaller force to move a heavier load. In this case, the objective is to move the object slightly, which suggests a preference for a greater mechanical advantage that would require less force for a given movement.
- First class lever (Option a) has equal force and resistance arms (both 10 units), resulting in no mechanical advantage. This lever type does not give a clear advantage in moving the object slightly with minimal effort.
- Second class lever (Option b) has a force arm of 20 units and a resistance arm of 10 units. This gives a mechanical advantage of 2, meaning that less force is required to move the object. This lever type is most effective when the goal is to move the object slightly using minimal effort.
- Third class lever (Option c) has a shorter force arm (10 units) and a longer resistance arm (20 units). This type of lever requires more effort to move the object, as it has a mechanical disadvantage.
Since you want to move the object slightly, the second class lever with a larger force arm will allow you to move the object with less effort. This makes it the best option for the given objective.