To calculate the acceleration, we can use the formula:

```

acceleration = (final velocity - initial velocity) / time

```

In this case, the initial velocity is 20 m/s, the final velocity is 30 m/s, and the time is 10 seconds. Plugging these values into the formula, we get:

```

acceleration = (30 m/s - 20 m/s) / 10 s

= 1 m/s^2

```

Therefore, the acceleration of the car is 1 m/s^2.