To indicate the direction and the strength of a force, we use an arrow. The length of the arrow indicates the magnitude of the force, and the head of the arrow points towards the direction in which the force acts.

For example, if we have a force of 10 Newtons acting in the east direction, we can represent it as:

```

>------- 10 N

```

In this case, the length of the arrow is 10 units (which represents the magnitude of the force), and the arrow is pointing towards the east (which represents the direction of the force).