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Difficulty: MediumLevers and Fulcrums

Match each mechanical tool or scenario with its correct lever classification and mechanical advantage (MA) characteristic.

  • Using a long pry bar pivoting on a wooden block near a heavy engine to lift itClass 1 lever; fulcrum is closer to the load, providing a mechanical advantage greater than 1.
  • Using a hand truck (dolly) tilting back over its bottom wheels to transport heavy cratesClass 2 lever; load is between fulcrum and effort, always providing a mechanical advantage greater than 1.
  • Using precision tweezers to position a small, lightweight screw in a circuit boardClass 3 lever; effort is between fulcrum and load, providing a mechanical advantage less than 1.
  • Two mechanics of equal weight balancing perfectly on a symmetrical seesawClass 1 lever; fulcrum is central, providing a mechanical advantage exactly equal to 1.

Answer

Pry bar matches to Class 1 (MA > 1); Hand truck matches to Class 2 (MA > 1); Tweezers match to Class 3 (MA < 1); Symmetrical seesaw matches to Class 1 (MA = 1).
Each tool utilizes a specific lever class based on the relative arrangement of the Fulcrum, Load, and Effort. By identifying which component is positioned in the middle, we determine the correct class. The ratio of the effort arm to the load arm then dictates whether the mechanical advantage is greater than, equal to, or less than 1.

Step-by-Step Solution

1
Analyze the pry bar scenario to locate the relative positions of the fulcrum, effort, and load.
The fulcrum (wooden block) is between the effort (hands) and the load (engine), but closer to the load.
This configuration defines a Class 1 lever that is optimized for force multiplication.
2
Analyze the hand truck to identify its lever class.
The wheels act as the fulcrum at one end, the effort is applied at the opposite end (handles), and the load (crates) rests in the middle.
Having the load in the middle defines a Class 2 lever, which always provides a mechanical advantage greater than 1.
3
Examine how tweezers apply force.
The fulcrum is the joined end, the effort is applied by fingers pinching the middle, and the load is grasped at the opposite open end.
Having the effort in the middle defines a Class 3 lever, which trades force for precision and distance (MA < 1).
4
Evaluate the symmetrical seesaw scenario.
The fulcrum is directly in the center with equal distances to both applied forces.
This is a Class 1 lever where neither distance nor force is multiplied, meaning MA equals 1.

Key Concept

Lever Classifications and Mechanical Advantage
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Topics

Levers and Fulcrums

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