If a stone of mass 0.05 kg is thrown out a window of a train moving at a constant speed of 100 km/ h then magnitude of the net force acting on the stone is

Options

A. 0.5 N
B. zero
C. 50 N
D. 5 N

Answer

To solve the problem, we need to determine the net force acting on the stone after it is thrown out of the window of a moving train.

### Step-by-Step Solution:

1. **Identify the Forces Acting on the Stone:**
When the stone is thrown out of the window, the primary force acting on it is the force of gravity. The stone will also have an initial horizontal velocity due to the motion of the train, but this does not contribute to the net force acting on it.

2. **Calculate the Weight of the Stone:**
The weight (force due to gravity) can be calculated using the formula:
\[ F = m \cdot g \]
where:
- \( F \) is the weight,
- \( m \) is the mass of the stone (0.05 kg),
- \( g \) is the acceleration due to gravity (approximately \( 9.81 \, \text{m/s}^2 \)).

Plugging in the values:
\[ F = 0.05 \, \text{kg} \cdot 9.81 \, \text{m/s}^2 = 0.4905 \, \text{N} \]

3. **Determine the Net Force:**
Since the stone is in free fall after being thrown out, the only force acting on it is its weight. Therefore, the net force acting on the stone is equal to its weight.

Thus, the magnitude of the net force acting on the stone is:
\[ F_{\text{net}} = 0.4905 \, \text{N} \]

### Final Answer:
The magnitude of the net force acting on the stone is approximately **0.49 N** (rounded to two decimal places).

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