Answer:
679.2 m/s
Explanation:
The formula for the time of flight of a projectile is given as,
T = 2usinФ/g ......................... Equation 1
Where T = Time of flight, u = initial velocity, Ф = angle of projectile to the horizontal, g = acceleration due to gravity.
make u the subject of the equation
u = Tg/2sinФ....................... Equation 2
Given: T = 69 s, Ф = 30°
Constant: g = 9.8 m/s²
Substitute into equation 2
u = (69×9.8)/(2×sin30)
u = 679.2 m/s.
Hence the initial speed of the projectile is 679.2 m/s
