2D Motion with a missle/engines

[wallace13]

On a spacecraft two engines fire for a time of 505 s. One gives the craft an acceleration in the x direction of ax = 5.10 m/s2, while the other produces an acceleration in the y direction of ay = 7.30 m/s2. At the end of the firing period, the craft has velocity components of vx = 3610 m/s and vy = 4928 m/s. Find the magnitude and direction of the initial velocity. Express the direction as an angle with respect to the +x axis.



Vf= Vi +at

tan O= opp/adj

3610 m/s = Vi + (5.1 x 505)

Vi= 1034.5 m/s

tan O= 7.3/ 5.1
O= 55.06 degrees


the answer was incorrrect and I have no idea what else to do

 

[Kurdt]

You found the initial x component well enough but you didn't find the y component. You then need to find the magnitude (i.e. pythagoras) and then apply your tan formula to the initial speeds.