Understanding Zero Velocity
When analyzing motion in physics, the concept of velocity being zero can arise in various scenarios. Here’s a detailed breakdown to clarify this phenomenon.

Definition of Velocity
- Velocity is defined as the rate of change of displacement with respect to time.
- Mathematically, it is expressed as:
\[ v = \frac{\Delta x}{\Delta t} \]
where \( v \) is velocity, \( \Delta x \) is change in position, and \( \Delta t \) is change in time.

Conditions for Zero Velocity
- **No Change in Position**: If an object does not move from its initial position, the displacement (\( \Delta x \)) is zero. Hence, regardless of the time taken, the velocity remains:
\[ v = \frac{0}{\Delta t} = 0 \]
- **Instantaneous Velocity**: At a specific moment during motion, if the object is momentarily at rest, its instantaneous velocity is zero. This is common at the peak of a projectile’s trajectory.
- **Uniform Circular Motion**: In scenarios involving uniform circular motion, while the speed remains constant, at specific points (like the topmost point), the velocity can be considered zero momentarily in components.

Practical Example
- **Free Fall**: When an object is dropped and reaches the ground, at the moment of impact, its velocity can be considered zero before it begins to rebound.

Conclusion
Understanding when and why velocity equals zero is crucial in physics, especially in kinematics, as it indicates periods of rest or specific motion characteristics. Remember, zero velocity does not imply the absence of motion; rather, it describes a momentary state within a broader context of movement.