# Help with kinematic equations.

1. Sep 28, 2007

### pebbles

hello,
i'm having trouble with kinematic equations. i feel that i understand them, but when i get to a problem, i'm so confused. i can figure out what i have and what i don't have, but it's choosing the correct formula that is my main problem.

how do i know when to solve for what?

for example, i'm given speed of 25 m/s [acceleration is constant] and i know that the object comes to rest after 34 seconds and now i am asked to solve for distance

initial speed=25 m/s, final speed=0, time=34 s.

would i use x=1/2(final velocity + initial velocity)t?

2. Sep 28, 2007

### pebbles

what is constant acceleration, zero?

3. Sep 28, 2007

Yes, you should use equation $$\Delta$$x=1/2(Vf+ Vi)t
a=$$\Delta$$ V /$$\Delta$$ t or more specific a=dv/dt.