Projectile motion (magnitude and direction)

[blazeuofa]

Homework Statement

A projectile is fired at a speed of 45 m/s at an angle of 40 degrees above horizontal. Determine the magnitude and direction of its velocity 4 seconds later.

Homework Equations

ax=0 ay=-g

The Attempt at a Solution

 

[needlottahelp]

find the vy and the vx after 4 seconds and find the resultant vector.

 

[blazeuofa]

find the vy and the vx after 4 seconds and find the resultant vector.

yeah i don't get how to do that though

 

[needlottahelp]

oh hahah ok well
Given: vi= 45 m/s and t = 4
so vyi = sin (40) vi and vxi = cos (40) vi

and to find the speed in four seconds you use the kinematics equation
vyf = vyi + (ay) (t) and velocity in the horizontal remains constant since ax = 0

find those to values and vf = sqrt ( vyf^2 + vxf ^2)

Do you understand it? if not I'll try to explain it a bit more

 

[blazeuofa]

yeah i got it thanks