# Homework Help: Motions with zero launch angle.

1. Sep 15, 2011

### matt@USA

1. The problem statement, all variables and given/known data
A hot-air balloon rises from the ground with a velocity of (3.00m/s)y. A champagne bottle is opened to celebrate takeoff, expelling the cork horizontally with a velocity of (4.00m/s)x relative to the balloon. When opened, the bottle is 5.00m above the ground.

What is the initial velocity of the cork, as seen by an observer on the ground?

What is the speed of the cork, as seen by the same observer?

2. Relevant equations
I am just confused as to what is what. All I need help with is, is making sure I am correct. I would say y=5.0m, and x=0 correct? I would then say that Vnotx is 4.0m/s, and Vnoty is 3.0m/s?

3. The attempt at a solution

2. Sep 15, 2011

### matt@USA

3. Sep 15, 2011

### lewando

That is correct for part 1. By the way it's V-naught-x/y, or better: V0x, V0y.

4. Sep 15, 2011

### matt@USA

Is ymax not Vnaught^2(sin)^2theta/2(g)?

5. Sep 16, 2011

### lewando

I prefer the more readable and less ambiguous: ymax = (v02sin2Θ)/2g.