Here's why:

* Force: A force is a push or pull that can change an object's motion.

* Acceleration: Acceleration is the rate at which an object's velocity changes. Velocity includes both speed and direction.

Therefore, a force that causes an object to speed up is directly related to the object's acceleration.

Example:

* When you push a car, you apply a force. This force causes the car to accelerate, meaning its speed increases.