A balloon os mass 2 KG is rising up with an acceleration of `4m/s^2` . The upward force acting on the balloon is `(g = 10 ms^(-2)`

Options

A. 0.8 kgf
B. 2.8 kgf
C. 2.4 kgf
D. 2.0 kgf

Answer

To solve the problem of finding the upward force acting on a balloon with a mass of 2 kg that is rising with an acceleration of 4 m/s², we can follow these steps:

### Step-by-Step Solution:

1. **Identify the forces acting on the balloon**:
- The upward force (F) acting on the balloon.
- The downward force which is the weight of the balloon (W).

2. **Calculate the weight of the balloon**:
- The weight (W) can be calculated using the formula:
\[ W = m \cdot g \]
- Where:
- \( m = 2 \, \text{kg} \) (mass of the balloon)
- \( g = 10 \, \text{m/s}^2 \) (acceleration due to gravity)
- Therefore:
\[ W = 2 \, \text{kg} \cdot 10 \, \text{m/s}^2 = 20 \, \text{N} \]

3. **Apply Newton's second law of motion**:
- According to Newton's second law, the net force (F_net) acting on the balloon is given by:
\[ F_{\text{net}} = m \cdot a \]
- Where:
- \( a = 4 \, \text{m/s}^2 \) (acceleration of the balloon)
- Thus:
\[ F_{\text{net}} = 2 \, \text{kg} \cdot 4 \, \text{m/s}^2 = 8 \, \text{N} \]

4. **Set up the equation for the forces**:
- The net force acting on the balloon can also be expressed as:
\[ F - W = F_{\text{net}} \]
- Substituting the known values:
\[ F - 20 \, \text{N} = 8 \, \text{N} \]

5. **Solve for the upward force (F)**:
- Rearranging the equation gives:
\[ F = 8 \, \text{N} + 20 \, \text{N} = 28 \, \text{N} \]

6. **Convert the force to kgf (kilogram-force)**:
- To convert Newtons to kilogram-force, we use the conversion factor \( 1 \, \text{kgf} = 10 \, \text{N} \):
\[ F_{\text{kgf}} = \frac{28 \, \text{N}}{10 \, \text{N/kgf}} = 2.8 \, \text{kgf} \]

### Final Answer:
The upward force acting on the balloon is **28 N** or **2.8 kgf**.