Here's why:

* Newton's Second Law of Motion: This fundamental law states that the acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass.

* Acceleration and Velocity: Acceleration is the rate of change of velocity. If an object is accelerating, its velocity is changing.

* Force and Acceleration: Since force causes acceleration, and acceleration changes velocity, it follows that force always changes the velocity of an object.

Examples:

* Pushing a box: Applying force to a box makes it accelerate and change its velocity.

* Throwing a ball: The force of your throw changes the ball's velocity.

* Gravity: The force of gravity pulls objects towards the Earth, causing them to accelerate and change their velocity.

Important Note: While force *always* changes velocity, it's not the only factor that *can* change velocity. Velocity can also be changed by a change in direction, even if the speed remains constant.