How Do You Calculate Initial Velocity and Angle in Two-Dimensional Kinematics?

[zn23]

Homework Statement

Useful background for this problem can be found in Multiple-Concept Example 2. On a spacecraft two engines fire for a time of 871 s. One gives the craft an acceleration in the x direction of ax = 6.00 m/s2, while the other produces an acceleration in the y direction of ay = 5.68 m/s2. At the end of the firing period, the craft has velocity components of vx = 5800 m/s and vy = 6420 m/s. Find (a) the magnitude and (b) the direction of the initial velocity. Express the direction as an angle with respect to the +x axis.

Homework Equations

most likely the use of the 4 main kinematics equations

v2=v1+at
v2^2=v1^2+2ad
x=1/2(v1+v2)t
x=v1t+1/2at^2

The Attempt at a Solution

basically i have no idea where to begin in this question, its computer question and I keep getting the incorrect answer, if anybody has suggestions how to begin this problem that would be nice, like what wud i do with that time of 871 s?

 

[tiny-tim]

most likely the use of the 4 main kinematics equations

v2=v1+at
v2^2=v1^2+2ad
x=1/2(v1+v2)t
x=v1t+1/2at^2

Hi zn23!

You can forget equations involving x … there's no distance involved in this problem.

Hint: Find ∆Vx and ∆Vy, and then its' a simple vector addition problem .