Answer:
3.82 ms
Explanation:
The period of a wave is equal to the reciprocal of the frequency:

where f is the frequency.
In this problem, f = 262 Hz, so the period if this sound wave is

Mechanical energy is the answer
Answer:
Initial velocity will be 1.356 m/sec
Explanation:
Let the initial speed = u
Angle at which rubber band is launched = 37°
Horizontal component of initial velocity 
Time is given as t = 1.20 sec
Distance in horizontal direction = 1.30 m
We know that distance = speed × time
So time 


So initial velocity will be 1.356 m/sec
The earth is so round that we can run around it in five million days