The quantity, when measured from different inertial reference frames, remains the same , among the following is

Options

A. Force
B. Velocity
C. Displacement
D. Kinetic energy

Answer

To solve the problem, we need to determine which of the given quantities remains the same when measured from different inertial reference frames. The options provided are: force, velocity, displacement, and kinetic energy.

### Step-by-Step Solution:

1. **Understanding Inertial Reference Frames**:
- Inertial reference frames are those that are either at rest or moving at a constant velocity. The laws of physics are the same in all inertial frames.

2. **Analyzing Each Quantity**:
- **Force**:
- Force is defined as \( F = ma \) (mass times acceleration).
- Acceleration is dependent on the change in velocity, which varies between different frames. Therefore, force is frame-dependent.

- **Velocity**:
- Velocity is defined as the rate of change of displacement with respect to time (\( v = \frac{dx}{dt} \)).
- Since displacement and time can differ in different frames, velocity is also frame-dependent.

- **Displacement**:
- Displacement is the change in position of an object. It is also frame-dependent because the position of an object can vary based on the observer's frame of reference.

- **Kinetic Energy**:
- Kinetic energy is given by the formula \( KE = \frac{1}{2} mv^2 \), where \( m \) is mass and \( v \) is speed.
- Speed is the magnitude of velocity and is a scalar quantity. While velocity is frame-dependent, the speed (magnitude of velocity) can be calculated in such a way that it remains consistent across different inertial frames when considering the same object moving with the same mass.

3. **Conclusion**:
- Among the options, kinetic energy is the only quantity that remains the same when measured from different inertial reference frames. This is because mass is invariant and speed (as a scalar) does not change in value when calculated in different frames for the same object.

Thus, the correct answer is **Kinetic Energy**.

### Final Answer:
**Kinetic Energy**