The frequency of an oscillation is equal to the reciprocal of the period:

where
f is the frequency
T is the period
In our problem, the period is T=8.01 s, therefore the corresponding frequency is
Force exerted: 100
To find force you multiply the mass by acceleration. The formula is
F = Ma, and the SI unit for force is newtons.
Answer:
Time of flight = 4.08seconds
Horizontal component of initial velocity is 17.32m/s
Explanation: complete question( and the horizontal component of the initial velocity.)
The equation for time of flight of a projectile is given as T= 2u/g
T=( 2×20)/9.8
T= 40/9.8= 4.08seconds
Horizontal component of initial velocity Vix= Vi Costheta
Vix= 20× cos 30°
Vix= 20×0.8660
Vix= 17.32m/s