# How to calculate theoretical initial velocity?

1. Feb 10, 2012

### pill

I can do with just an equation, but if anyone is willing to help:
Target is 25.6 m away from canon
Initial Velocity = 16 m/s
Time = 2.6 s
Range = 26.7m
No air resistance

2. Feb 11, 2012

### PeterO

Is your problem that you have been told the initial velocity is 16 and you don't know how it was calculated?

3. Feb 11, 2012

### genericusrnme

Initial Velocity = 16 m/s

If you mean final then you're going to have to tell me what this Range quantity is

4. Feb 11, 2012

### pill

To be honest, I'm not too sure. My instructions state, "Calculate the theoretical initial velocity (no air resistance) required to impact a target with the distance you used in the simulation." I actually messed up when typing the original post: range quantity is the same as target (25.6 m).

5. Feb 11, 2012

### pill

For the most part, yes. I used an online simulation for this lab and just continually changed the value of the initial velocity until it hit the target.

6. Feb 11, 2012

### PeterO

I we look at your original data
Target is 25.6 m away from canon
Initial Velocity = 16 m/s
Time = 2.6 s
Range = 26.7m
No air resistance

and just ignire that initial velocity figure, we know that it covered 25.6 m ( horizintally) in 2.6 seconds - so the horizontal component will be a little less than 10m/s

SInce it took 2.6 seconds to get there, it spent 1.3 seconds gaining height, then 1.3 seconds coming back down.
Standard analysis of vertical motion will tell you how fast it was travelling vertically. Add those two components together using pythagorus and you will get the answer - who knows; it might even be 16 !

7. Feb 12, 2012

### pill

Thanks! This made is a bit more clear to me. I found got this equation, and your description made it make sense:
Vx=16cos(∡)=26.7m/2.6s
Vy=√(256-(26.7m/2.6s)²)
V=16=√(26.7m/2.6s)²+Vy²

8. Apr 22, 2012

### moxi

Hi, I'm having the same issue and was wondering where you found your final formula? Any help is greatly appreciated!!!!