In which of the following cases , the observer is in intertial frame?

Options

A. A child revolving in a merry-go-round
B. A driver in a car moving with a constant velocity
C. A pilot is an aircraft which is taking off
D. a passenger in a train which is showing down to stop

Answer

To determine in which of the following cases the observer is in an inertial frame, we need to understand the concept of an inertial frame of reference. An inertial frame is one where an observer is either at rest or moving with a constant velocity, meaning there is no acceleration acting on the observer. If an accelerometer is attached to the observer, it will read zero in an inertial frame.

Let's analyze each option step by step:

1. **A child revolving in a merry-go-round**:
- In this case, the child is moving in a circular path. The direction of the child's velocity is continuously changing, which means there is a centripetal acceleration acting on the child. Since there is acceleration, this is not an inertial frame.
- **Conclusion**: This option is **not** an inertial frame.

2. **A driver in a car moving with a constant velocity**:
- Here, the car is moving at a constant speed in a straight line. Since the velocity is constant, there is no acceleration acting on the driver. If an accelerometer is attached to the driver, it would read zero.
- **Conclusion**: This option **is** an inertial frame.

3. **A pilot in an aircraft taking off**:
- During takeoff, the aircraft is accelerating upwards. This means the pilot experiences a change in velocity. Therefore, there is a non-zero acceleration acting on the pilot. An accelerometer would not read zero in this case.
- **Conclusion**: This option is **not** an inertial frame.

4. **A passenger in a train which is slowing down to stop**:
- In this scenario, the train is decelerating, which means the passenger is also experiencing a change in velocity. Thus, there is a non-zero acceleration acting on the passenger. An accelerometer would not read zero.
- **Conclusion**: This option is **not** an inertial frame.

Based on the analysis, the only case where the observer is in an inertial frame is:

**Final Answer**: The driver in a car moving with a constant velocity (Option 2).

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