A light-rail commuter train accelerates at a rate of 1.35 m/s2. how long does it take to reach its top speed of 80.0 km/h, starting from rest?

To answer this question, you need to convert the km/hour unit into m/s2 so it can be divided by the train acceleration rate. The calculation would be: 80 km/hour * 1000m/km * 1hour/3600second = 22.22m/s.

If the initial speed is zero, then the time needed for the train to reach that speed is: (22.22m/s) / (1.35m/s2) = 16.46 second