Kinematics (rectilnear motion) simple

[whynot314]

Ball 1 is launched with an initial vertical velocity v1=160 ft/sec. Three seconds later, ball 2 is launched with an initial velocity v2. determine v2 if the balls are to collide at an altitude of 300ft.


not sure where I am going wrong, do I have my limits correct?[URL=http://s1341.photobucket.com/user/nebula-314/media/20131222_191532_zpsf76c1ab5.jpg.html][PLAIN]http://i1341.photobucket.com/albums/o745/nebula-314/20131222_191532_zpsf76c1ab5.jpg[/URL][/PLAIN]

 

[whynot314]

v2 being initial velocity.

 

[Konoha]

I'm not sure what you're doing here, but if I were you I would use the following equation to calculate t for the first ball to reach 300ft, then using that t minus 3 (because the 2nd ball was launch 3 seconds later) and the same equation I would calculate v2.

\Deltax= \frac{1}{2}at^{2}+v_{0}t

Just remember that here we take upside direction to be positive, hence a=-g and if you are measuring distance in ft you should use g=32.17 ft/s^2 , or convert ft to meter and use g=9.8 m/s^2

Let me know how it goes :)

 

[whynot314]

Oh i was trying to derive that equation, and perhaps save some steps.

 

[whynot314]

But your solution did help a lot thanks.

 

[Konoha]

oh I see! I guess sometimes it's just easier to stick to the basics!

No problem at all, happy to help