1. Applying a Force:

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

* Acceleration: Acceleration is the rate of change of velocity. Therefore, applying a force to an object will cause it to accelerate, which means its speed will change.

* Examples:

* Pushing a cart: Applying force to the cart makes it move faster.

* Braking a car: Applying force through the brakes slows the car down.

* Throwing a ball: Applying force to the ball increases its speed.

2. Changing the Direction of Motion:

* Velocity: Velocity is a vector quantity, meaning it has both magnitude (speed) and direction.

* Changing Direction: Even if the speed remains constant, if the direction of motion changes, the velocity changes, and therefore the speed also changes.

* Examples:

* A car turning a corner: The car's speed might remain the same, but the direction changes, resulting in a change in velocity and a change in speed.

* A ball swinging in a circle: The ball's speed might remain constant, but its direction is constantly changing, resulting in a change in velocity and a change in speed.

In summary, the speed of an object can be changed by applying a force that causes acceleration, or by changing the direction of motion, which changes the velocity.