Answer:
Step-by-step explanation:
At the top of the trajectory , the velocity of the projectile is equal to the horizontal component of the initial velocity .
Given the range of the projectile is 49 m and its time of flight is 3.9 s that means it covers the range in 3.9 s . Horizontal displacement is equal to range which is 49 m and horizontal displacement is due to horizontal component of initial velocity .
So horizontal component of initial velocity = horizontal displacement / time
= 49 / 3.9 = 12.56 m /s
Hence velocity at the top = 12.56 m /s .