* Velocity is a measure of how fast an object is moving and in what direction. It's a vector quantity.

* Acceleration is the rate of change of velocity over time.

Scenario:

Imagine a ball thrown straight up in the air. At the very top of its trajectory, for a split second:

* Velocity is zero: The ball momentarily stops moving before falling back down.

* Acceleration is non-zero: Gravity is still acting on the ball, pulling it downwards. This means the ball is still changing its velocity (even though it's momentarily zero), and therefore has an acceleration.

Other Examples:

* A car at a red light: The car is stationary (zero velocity), but the driver is pressing on the brakes to keep it from moving forward. This braking force causes a negative acceleration.

* A ball rolling on a horizontal surface then hitting a wall: The ball will have a moment of zero velocity when it collides with the wall, but the force from the wall causes an acceleration to change its direction and speed.

Key Point: Zero velocity doesn't mean zero acceleration. Acceleration is about *change* in velocity, not the velocity itself.