9.8N is equal to

Options

A. 1kg f
B. 1 kg wt
C. both a and b
D. neither a nor b

Explanation

To determine what 9.8 N is equal to, we need to understand the relationship between Newtons (N), kilograms (kg), and the concept of weight.

### Step-by-Step Solution:

1. **Understanding the Units:**
- A Newton (N) is the SI unit of force. It is defined as the force required to accelerate a mass of 1 kilogram at a rate of 1 meter per second squared (m/s²).

2. **Weight Formula:**
- The weight (W) of an object is given by the formula:
\[ W = m \cdot g \]
where \( m \) is the mass in kilograms (kg) and \( g \) is the acceleration due to gravity.

3. **Acceleration Due to Gravity:**
- On the surface of the Earth, the acceleration due to gravity (g) is approximately 9.8 m/s².

4. **Calculating Weight of 1 kg:**
- If we take a mass of 1 kg, the weight can be calculated as:
\[ W = 1 \, \text{kg} \cdot 9.8 \, \text{m/s}^2 = 9.8 \, \text{N} \]
- This means that the weight of a 1 kg mass is 9.8 N.

5. **Understanding kgf (kilogram-force):**
- 1 kgf (kilogram-force) is defined as the force exerted by gravity on a mass of 1 kg at the surface of the Earth, which is also equal to 9.8 N.

6. **Conclusion:**
- Therefore, 9.8 N is equal to both 1 kgf and the weight of a 1 kg mass.

### Final Answer:
- The correct option is **3**: both A (1 kgf) and B (1 kg weight) are equal to 9.8 N.

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