1. Convert Units

* Acceleration: 2.0 km/hr² needs to be converted to m/s².

* 1 km = 1000 m

* 1 hour = 3600 seconds

* 2.0 km/hr² = (2.0 * 1000 m) / (3600 s)² ≈ 0.00154 m/s²

* Initial Velocity: 20 km/hr needs to be converted to m/s.

* 20 km/hr = (20 * 1000 m) / (3600 s) ≈ 5.56 m/s

* Time: 30 seconds is already in the correct units.

2. Use the Kinematic Equation

We'll use the following kinematic equation to find the final velocity (v):

v = u + at

Where:

* v = final velocity

* u = initial velocity

* a = acceleration

* t = time

3. Plug in the Values

* v = 5.56 m/s + (0.00154 m/s²) * 30 s

* v ≈ 5.56 m/s + 0.0462 m/s

* v ≈ 5.61 m/s

4. Convert Back to km/hr (Optional)

* 5.61 m/s = (5.61 * 3600 s) / 1000 m ≈ 20.19 km/hr

Therefore, after 30 seconds, the train's velocity will be approximately 5.61 m/s or 20.19 km/hr.