# Homework Help: Kinematics, volcano eruption speed problem

1. Sep 1, 2008

### rsfancy

A volcano launches a lava bomb straight upward with an initial speed of 28 m/s.

a)Taking upward to be the positive direction, find the speed of the lava bomb 2.0 seconds after it is launched.

b)Taking upward to be the positive direction, find the direction of motion of the lava bomb 2.0 seconds after it is launched.
Upward or Downward?

c)Taking upward to be the positive direction, find the speed of the lava bomb 3.0 seconds after it is launched.

d)Taking upward to be the positive direction, find the direction of motion of the lava bomb 2.0 seconds after it is launched.
Upward or Downward?

I know this stuff is pretty basic, but my prof. wont explain or give us examples of anything,so I'm really confused. Anything to point me in the right direction would be helpful. Thank you.

2. Sep 1, 2008

### chislam

I'm going to specifically talk about part a, and then after you understand part a, the rest should be easy.

Ok, you have 3 knowns and you are searching for 1 unknown. Your knowns include: initial velocity, acceleration and time. Your unknown is the instantaneous velocity at a specified time. Now, what formula matches your knowns and unknown?

3. Sep 1, 2008

### rsfancy

Wow, thank you very much. That definitely helped me see what was going on. I did get confused at first when you said that acceleration was known, and I did figure it would be gravity but the problem didnt explicitly state we should take into consideration, and I thought it would if we were meant to, as it did with the previous problems and that was my single problem with all of this........I cant even begin to explain how retarded I feel.

Thanks a lot for your help!!