Answer
The girl is using a first-class lever mechanism with the oar. She applies force at the handle (effort), and the oar blade exerts force on the water (load). The mechanical advantage is greater than one because she holds the oar near the handle, increasing the effort arm. To gain more mechanical advantage, she should hold the oar closer to the handle.
Solution
Certainly! Let's address each part of your question systematically.
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### a. **Identify the mechanism the girl in Figure 3.1 uses.**
**Answer:**
The girl is using a **lever mechanism**, specifically a **first-class lever**.
**Explanation:**
A lever consists of a rigid beam or rod pivoted at a fixed hinge called the fulcrum. In a **first-class lever**, the fulcrum is positioned between the input force (effort) and the output force (load). An oar used in rowing is a classic example of a first-class lever, where the pivot point is the oarlock, the rower applies force at one end, and the load is applied at the other end to propel the boat.
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### b. **Identify the input force (effort) and the output force (load) of the mechanism.**
**Answer:**
- **Input Force (Effort):** The force applied by the girl on the **handle** of the oar.
- **Output Force (Load):** The force exerted by the **oar blade** against the water to propel the boat forward.
**Explanation:**
In the lever mechanism:
- The **effort** is the force that the girl exerts, typically applied farther from the fulcrum to maximize leverage.
- The **load** is the resistance force that the oar exerts on the water, which moves the boat. The placement of these forces relative to the fulcrum determines the mechanical advantage of the lever.
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### c. **Is the mechanical advantage of the mechanism greater than one ( \( >1 \) ), equal to one (\( =1 \)), or less than one (\( <1 \))? Explain.**
**Answer:**
The **mechanical advantage (MA)** of the mechanism is **greater than one** (\( MA > 1 \)).
**Explanation:**
Mechanical advantage is calculated as the ratio of the length of the effort arm to the length of the load arm:
\[
MA = \frac{\text{Length of Effort Arm}}{\text{Length of Load Arm}}
\]
In a first-class lever like the oar:
- If the **effort arm** (distance from fulcrum to where the girl applies force) is longer than the **load arm** (distance from fulcrum to the oar blade), the MA is greater than one. This means the girl can exert a smaller input force to achieve a larger output force, making it easier to propel the boat.
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### d. **By looking at the way the girl holds the oar, explain how she should hold the oar so that she will gain more mechanical advantage.**
**Answer:**
To gain **more mechanical advantage**, **the girl should hold the oar as far from the fulcrum as possible**, meaning she should position her hands closer to the handle end of the oar.
**Explanation:**
Holding the oar farther from the fulcrum increases the length of the **effort arm**. According to the mechanical advantage formula:
\[
MA = \frac{\text{Length of Effort Arm}}{\text{Length of Load Arm}}
\]
A longer effort arm (holding the oar near the handle) relative to the load arm (the distance from the fulcrum to the oar blade) results in a higher MA. This setup allows the girl to apply less force to achieve the same propulsive effect, making rowing more efficient and less physically demanding.
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**Summary:**
- **Mechanism:** First-class lever (the oar).
- **Effort and Load:** Effort is applied at the handle; load is exerted by the oar blade on the water.
- **Mechanical Advantage:** Greater than one due to a longer effort arm.
- **Optimal Oar Handling:** Hold the oar near the handle to maximize mechanical advantage.
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Reviewed and approved by the UpStudy tutoring team
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