A person has a box of weight 20 kg. The energy of the box when he keeps the box in his hand for 5 minutes is:

Options

A. 100J
B. 200J
C. 6000J
D. zero

Answer

To solve the problem, we need to determine the energy of a box weighing 20 kg when held in hand for 5 minutes. We will analyze the situation in terms of kinetic energy and potential energy.

### Step-by-Step Solution:

1. **Identify the Type of Energy:**
- The box can have two types of energy: kinetic energy (due to motion) and potential energy (due to its position).

2. **Kinetic Energy Calculation:**
- Kinetic energy (KE) is given by the formula:
\[ KE = \frac{1}{2} mv^2 \]
- Here, \(m\) is the mass of the box (20 kg) and \(v\) is its velocity. Since the person is holding the box still (not moving), the velocity \(v = 0\).
- Therefore, the kinetic energy becomes:
\[ KE = \frac{1}{2} \times 20 \, \text{kg} \times (0)^2 = 0 \, \text{J} \]

3. **Potential Energy Calculation:**
- Potential energy (PE) is given by the formula:
\[ PE = mgh \]
- Here, \(g\) is the acceleration due to gravity (approximately \(9.81 \, \text{m/s}^2\)) and \(h\) is the height above a reference point. If we assume the box is held at a height close to the ground, we can consider \(h \approx 0\).
- Thus, the potential energy becomes:
\[ PE = 20 \, \text{kg} \times 9.81 \, \text{m/s}^2 \times 0 = 0 \, \text{J} \]

4. **Total Energy Calculation:**
- The total mechanical energy (E) of the box is the sum of its kinetic and potential energy:
\[ E = KE + PE = 0 \, \text{J} + 0 \, \text{J} = 0 \, \text{J} \]

5. **Conclusion:**
- The energy of the box when held in hand for 5 minutes is \(0 \, \text{J}\).

### Final Answer:
The energy of the box when held in hand for 5 minutes is **0 Joules**.

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