Why do you push an object closer to scissors (fulcrum) when you want to cut an object which is hard?
Pushing an object closer to the scissors' fulcrum decreases the load arm. In a lever, the distance of the load from the fulcrum is the load arm, and the distance of the effort is the effort arm.
According to the principle of levers, effort × effort arm = load × load arm. The mechanical advantage of the lever is the ratio of the effort arm to the load arm.
By reducing the load arm, the mechanical advantage increases. This means that for the same applied effort, a much larger force is applied on the load. This larger force helps overcome the resistance of hard objects, making them easier to cut.
Explanation
The textbook context establishes the principle of levers where effort × effort arm = load × load arm, and mechanical advantage = effort arm / load arm. When cutting a hard object, a larger force is needed on the load. By moving the object closer to the fulcrum, the load arm decreases. Since mechanical advantage is inversely proportional to the load arm, reducing the load arm increases the mechanical advantage. This allows the scissors to apply a much larger force on the load with the same amount of effort, making it possible to cut through hard materials.
Solution Steps
Step 1: Identify that moving the object closer to the fulcrum reduces the load arm.
Step 2: Apply the lever principle: effort × effort arm = load × load arm.
Step 3: Relate to mechanical advantage = effort arm / load arm.
Step 4: Conclude that a smaller load arm increases mechanical advantage, allowing a larger force to be applied on the load for the same effort.