Answer: I think, the number of oscillations in a given period of time.
Explanation: Well I guess because in a period time is known as the rate of occurrence of the wave. Hope this helps!
To calculate the initial velocity of the bike, we use the following equation
.
or

Here, u is initial velocity, v is final velocity, t is the time and d is the distance covered by bike.
Given,
,
and
.
Substituting these values in above equation, we get
.
Thus, the initial velocity of the bike is 1.2 m/s.