# Homework Help: Velocity vectors

1. May 4, 2013

### Robertoalva

1. The problem statement, all variables and given/known data

An object is moving in the x direction at 1.6 m/s when it is subjected to an acceleration given by a = 0.52 j m/s2. What is its velocity vector after 4.1 s of acceleration?

2. Relevant equations

v= vxi +vyj

3. The attempt at a solution[/b
I got for the i vector 1.6 m/s because it said that that was the x velocity, and for the y velocity I just multiplied the time and the acceleration vector and it gave me 2.13 m/s and both are right but I don't know why, i need someone to explain me why please.

2. May 4, 2013

### Henriamaa

Independence of directions

Remember that the things that happen in the x and y directions are completely independent of each other. Thus the acceleration in the y direction( which is equivalent to applying a force in y direction) only affects whatever is happening in the y direction. The object has velocity in x direction which is given to you but that is not affected by what happens in the y direction. On the other hand in the y direction the initial velocity $v_{oy}$ is zero, so if you apply a constant force ( or introduce constant acceleration) the kinematics equation you are really applying is $v_y=v_{oy} + a_yt$.
Hope this helps

Last edited: May 4, 2013
3. May 4, 2013

### BruceW

yep. it works because you can think of the equations for x motion as independent of the equations for y motion.

4. May 4, 2013

### Robertoalva

thanks now i know what happens! thanks for the tips also!