To find the acceleration of the bicycle rider, we are going to use the acceleration formula: 
where
is the acceleration
is the initial speed
is the final speed
is the time
We know from our problem that increases his speed from 5 m/s to 15 m/s in 10 seconds, so his initial speed is 5 m/s and his final speed is 15 m/s; therefore,
, 
, and
. Lets replace those values in our formula:
We can conclude that the acceleration of the bicycle rider 1 m/s^2
where
We know from our problem that increases his speed from 5 m/s to 15 m/s in 10 seconds, so his initial speed is 5 m/s and his final speed is 15 m/s; therefore,
We can conclude that the acceleration of the bicycle rider 1 m/s^2