Initial Velocity Question

1. MaNiFeST

36
Ok So if I were to launch a waterballoon with a waterballoon launcher VERTICALLY , how could I find out the Initial Velocity With OUT a stop watch? My other supplies include a meter stick

2. Cyrus

Are you familiar with conservation of energy?

3. MaNiFeST

36
This is for a lab at school and you get Extra Credit if you can figure out the first part without a stop watch. Would i have to weigh it? And sorry, im not familiar with conservation of energy

4. Cyrus

Ok, are you familiar with the equations of motion?

5. MaNiFeST

36
I am familiar with the equations for angles ( sin, cos), displacement in X,Y , etc,, for constant/non constant velocities and Trajectories

6. Cyrus

Look through them and try to find one that involves the parameters you think are going to be important and post it.

7. MaNiFeST

36
This isnt really a homework question but w/e

Thanks again

8. MaNiFeST

36
Well if I am shooting an object vertically then Displacment X will be 0m, and
Vy = Vo * sin(90) because the degrees will be 90
VFy = 0 m/s

Thats about all the variables i know atm

Im unsure of which equation to use

Last edited: Nov 4, 2006
9. Cyrus

Well, dont solve any equations yet, just look for some that might be useful, and well work from there.

10. MaNiFeST

36
Would this work
VFy^2 = VOy^2 + 2a*Displacment Y

11. Cyrus

Aha, you are on to something. Keep going.

12. MaNiFeST

36
Displacment Y = {(Vo^2+sin(2*angle)} / g

Only other one i know that doesnt involve time

Last edited: Nov 4, 2006
13. Cyrus

where did this come from? You were on the right track before. Maybe you should take a closer look at your first equation.

14. MaNiFeST

36
its equation for X or Y displacment
I am looking for Initial Velocity (Vo) and those two are the only ones that do not include time because i wont have a stop watch when doing this experiment

15. Cyrus

Yes, look at your first equation, and you tell me what each of those terms mean.

16. MaNiFeST

36
VFy^2 = VOy^2 + 2a*Displacment Y
I am looking for Initial Velocity and not just VOy
Final Velocity of Y = is 0 m/s in this case
VOy^2 = is unknown
a = 9.81m/s^2 in this case
Displacment Y = is also unknown

17. Cyrus

Ok, we need to get this terminology straight.

$$V_{fy}$$ means the final velocity in the y direction.

$$V_{oy}$$ means the initial velocity in the y direction.

Does this help at all?

Yes, that's correct. Now when does this occur?

18. MaNiFeST

36
VFy That occurs when the object stops right before it comes back down
I Know what the terminology means,

19. Cyrus

How would a ruler be useful given this information? What is the value of Vfy?

20. MaNiFeST

36
Thats the thing, I have almost no idea

Know someone interested in this topic? Share this thead via email, Google+, Twitter, or Facebook

Have something to add?