Remember, if an object is starting
from rest (zero m/s) then Vo=0 and if an object comes to rest, then Vf=0
DX=((Vo+Vf)t)/2
| Xf-Xo=Vt, where v=average velocity, or Vavg | |
| Vavg=(Vf+Vo)/2 because to average is to sum and divide by # total | |
| if we insert second equation into first one (where V is), | |
| we get Xf-Xo=((Vf+Vo)t)/2 | |
| introduce 2nd equation (from line
2 above)Vf=Vo+at insert
this into third equation above,
(1 box above this one) |
|
| get Xf-Xo=((Vo+at+Vo)t)/2 | |
| clean it up a bit | |
| get, Xf-Xo=(2Vot+at²)/2 | |
| which is the same as 2Vot/2 + at²/2 | |
| so we cancel out a couple of 2's, | |
| and get Xf-Xo=Vot+at²/2 | |
| quite often we are asked for some final position, so physics books usually write the equation as | |
| Xf=Xo+Vot+at²/2 |