Find Velocity of Ball After 3 Seconds

[look416]

Homework Statement

A ball is projected horizontally from the top oF A CLIFF WOTH SPEED U. iF AIR RESISTANCE IS NEGLECTED AND G IS ASSUMED to be 10 ms^-2, the velocity of the ball is found to be 50ms^-2, 3 seconds later. What is the value of u

Homework Equations

s=ut+1/2at²
s=vt
v²=u²+2as
v=u+at

The Attempt at a Solution

well the problem is i do not know to use which components either x or y
if i use x, but in projectile motion and Newton 1st law, the speed of x will not change as there is no other force to push or pull the ball
however, usually we use the initial speed for x only, and for y is 0
so how X.X

 

[look416]

well no1 can solve it ? ==

 

[rl.bhat]

Ball moves horizontally without any change in its velocity U
Ball falls vertically withe zero initial velocity.
What is its velocity V in the vertical direction after 3 seconds?
U and v are perpendicular to each other.
What is the resultant of these two velocities?
Equate this resultant velocity to 50 ms^-1. , and find U

 

[look416]

well this is what i have done
v=u+at
v=0+(9.8)x(3)
v=\frac{147}{5}
using Pythagorus theorem,
a²+b²=c²
(\frac{147}{5})²+b²=50²
so the b=40.44
yep i got the answer thanks so much