Which diagram correctly shows the reading of a spring scale when weighing a 200 g mass?

Problem Analysis:

The task involves determining which diagram best represents the correct reading on a spring scale when weighing a 200 g mass. To solve this, we need to understand the relationship between mass, weight, and the readings on a spring scale.

#### Key Concepts:
1. Mass vs. Weight:
- Mass is a measure of the amount of matter in an object (measured in grams or kilograms).
- Weight is the force exerted on an object due to gravity (measured in newtons, N).
- The relationship between mass and weight is given by the formula:
\[
\text{Weight} = \text{Mass} \times \text{Acceleration due to gravity}
\]
On Earth, the acceleration due to gravity is approximately \( g = 9.8 \, \text{m/s}^2 \).

2. Spring Scale Reading:
- A spring scale measures the weight of an object, not its mass.
- The scale is calibrated in newtons (N), so the pointer indicates the weight in newtons.

#### Given Information:
- The mass to be weighed is \( 200 \, \text{g} \).
- We need to calculate the corresponding weight in newtons and match it with the correct diagram.

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Step-by-Step Solution:

#### Step 1: Convert the mass to kilograms.
The mass is given as \( 200 \, \text{g} \). To use the formula for weight, we need to convert grams to kilograms:
\[
200 \, \text{g} = \frac{200}{1000} \, \text{kg} = 0.2 \, \text{kg}
\]

#### Step 2: Calculate the weight using the formula.
The weight \( W \) is given by:
\[
W = \text{Mass} \times g
\]
Substitute the values:
\[
W = 0.2 \, \text{kg} \times 9.8 \, \text{m/s}^2 = 1.96 \, \text{N}
\]

#### Step 3: Match the calculated weight to the diagrams.
The spring scale in the diagrams is calibrated in newtons. The pointer should indicate a value close to \( 1.96 \, \text{N} \).

- Diagram (1): The pointer is at \( 1 \, \text{N} \).
- Diagram (2): The pointer is at \( 2 \, \text{N} \).
- Diagram (3): The pointer is at \( 3 \, \text{N} \).
- Diagram (4): The pointer is at \( 4 \, \text{N} \).

Since \( 1.96 \, \text{N} \) is closest to \( 2 \, \text{N} \), the correct diagram is Diagram (2).

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Final Answer:

\[
\boxed{\text{Choice 2}}
\]