The record for a marathon is 1 h, 21 min, 21 s. The marathon distance is 25.84 km. Determine the average speed in m/s of a runner achieving this record.

To determine the average speed of a runner achieving this record, we need to convert the time and distance into a common unit.

First, let's convert the time from hours, minutes, and seconds into seconds. We have:

1 hour = 60 minutes = 60 * 60 = 3600 seconds
21 minutes = 21 * 60 = 1260 seconds
21 seconds = 21 seconds

Therefore, the total time in seconds is 3600 + 1260 + 21 = 4881 seconds.

Next, let's convert the distance from kilometers to meters. We know that 1 kilometer is equal to 1000 meters. So, the marathon distance of 25.84 km is equal to 25.84 * 1000 = 25840 meters.

Now that we have the time in seconds and the distance in meters, we can calculate the average speed. The formula for average speed is:

Average Speed = Distance / Time

Plugging in the values, we have:

Average Speed = 25840 meters / 4881 seconds

Dividing the distance by the time, we get:

Average Speed ≈ 5.29 m/s

Therefore, the average speed of a runner achieving this record is approximately 5.29 meters per second.