Which of these is a second-class lever?

1. Analyze the question

The question asks us to identify a second-class lever from the given options. To solve this, we must understand the classification of levers based on the relative positions of the Fulcrum (F), Load (L), and Effort (E).

2. Explain the concept

Levers are classified into three types based on which component is in the middle:

• First-class lever: The Fulcrum is between the Effort and the Load (F is in the middle). Examples: See-saw, scissors, pliers, claw hammer (when pulling a nail).
• Second-class lever: The Load is between the Fulcrum and the Effort (L is in the middle). This type of lever always provides a mechanical advantage greater than 1, making it easier to lift heavy weights. Examples: Wheelbarrow, nutcracker, bottle opener.
• Third-class lever: The Effort is between the Fulcrum and the Load (E is in the middle). Examples: Sugar tongs, tweezers, fishing rod.

3. Show the solution

Let's evaluate each option:

• A. Sugar tongs: The effort is applied in the middle, between the fulcrum (the hinge) and the load (the sugar cube). This is a third-class lever.
• B. Claw hammer: When used to pull a nail, the fulcrum is the head of the hammer, the load is the nail, and the effort is applied at the handle. The fulcrum is in the middle. This is a first-class lever.
• C. Plier: The fulcrum is the hinge, the effort is applied at the handles, and the load is at the jaws. The fulcrum is in the middle. This is a first-class lever.
• D. Wheelbarrow: The fulcrum is the wheel axle, the load is the material in the bucket, and the effort is applied at the handles. The load is in the middle, between the fulcrum and the effort. This is a second-class lever.

4. Identify the answer

Based on the classification, the wheelbarrow is the only second-class lever listed.

5. Tip

To remember the order of levers, use the mnemonic "FLE":

• F (1st class): Fulcrum in the middle.
• L (2nd class): Load in the middle.
• E (3rd class): Effort in the middle.