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Questions and Answers
Describe a lever.
Describe a lever.
A simple machine consisting of a bar that rotates around a fixed point.
The fixed point of a lever is called the _____.
The fixed point of a lever is called the _____.
fulcrum
Explain why a hammer makes it easier to pull a nail out of a board.
Explain why a hammer makes it easier to pull a nail out of a board.
It changes the direction of the force applied to the hammer—the hand pushes down on the handle while the claw end of the hammer head pulls up.
Levers that change the direction of the force are:
Levers that change the direction of the force are:
The only class of lever that can have an ideal mechanical advantage equal to 1 is a _____ class lever.
The only class of lever that can have an ideal mechanical advantage equal to 1 is a _____ class lever.
The class of lever that has the fulcrum at one end and the input force close to the fulcrum is a _____ class lever.
The class of lever that has the fulcrum at one end and the input force close to the fulcrum is a _____ class lever.
Examples of first-class levers include:
Examples of first-class levers include:
All of the following are third-class levers except:
All of the following are third-class levers except:
A second class lever always has an ideal mechanical advantage less than 1.
A second class lever always has an ideal mechanical advantage less than 1.
A third class lever always applies the output force over a greater distance than the input force.
A third class lever always applies the output force over a greater distance than the input force.
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Study Notes
Understanding Levers
- A lever is a simple machine made of a bar that pivots around a fixed point known as the fulcrum.
- Levers can change the direction of an applied force, making tasks easier (e.g., using a hammer to pull a nail).
Types of Levers
- First-class levers: Fulcrum is positioned between the input force and output force; can achieve an ideal mechanical advantage of 1. Examples include see-saws.
- Second-class levers: Fulcrum is at one end with the load in the middle; can achieve a mechanical advantage greater than 1.
- Third-class levers: Input force is applied between the fulcrum and the output force; they always apply output force over a greater distance than input force.
Key Class Characteristics
- First-class levers include examples such as see-saws; they can easily change the direction of the applied force.
- Third-class levers include tools like brooms and hockey sticks, while wheelbarrows are not classified as such.
Mechanical Advantage Insights
- Not all second-class levers have an ideal mechanical advantage less than 1; this statement is false.
- A third-class lever will always move the output force over a greater distance than the input force, indicating a distinct mechanical property.
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