Finding magnitude of horizontal velocity

[hello115897]

Homework Statement

A cannonball is launched horizontally from the top of a tall cliff with a horizontal speed of 45.0 m/s. The trajectory of the ball is shown in the diagram at the right. Determine the magnitude of the horizontal velocity and the vertical velocities of the cannonball after each of the 1.0 second time intervals. Use -9.8 m/s/s to calculate the values.

find horizontal velocity for t=1 second, t=2 seconds, t=3 seconds, t=4 seconds

Homework Equations

kinematic equations

The Attempt at a Solution

i think i would use the equation d=vit+1/2at^2
so i'd do 1/2(9.8)(1)^2
so it would be 4.9?

 

[method_man]

The Attempt at a Solution

i think i would use the equation d=vit+1/2at^2
so i'd do 1/2(9.8)(1)^2
so it would be -4.9?

It's minus because it is faced downward ---> v_y=v_y0t-(1/2)*g*t²

 

[hello115897]

im still not getting the right answer...

 

[method_man]

im still not getting the right answer...

Ups, I'm so sorry. That was the formula for displacement-d. The formula for vertical velocity would be:
v_y=-g*t.