# D=1/2 *a*t^2

1. Feb 21, 2006

### JEscribir

I need to find the height a rocket travels(bottle rocket). If I use this equation, ignoring air resistance, etc... I should use a stop watch from the time of launch till it hits the ground equaling t. a=9.81 m/s.

Is that the correct way to use the formula for this excerise?

Is there another way I should use it?

Is there another formula or method to find the height?, if so what?

--Thanks

2. Feb 21, 2006

### topsquark

It certainly isn't a bad way to do it. Just remember that it takes only half the time to get to max height as it does to get back to the ground.

BTW: I wouldn't be me if I didn't say something...I'm a real prig when it comes to units...The magnitude of a is 9.81 m/s^2, NOT m/s. :surprised

-Dan

3. Feb 21, 2006

### JEscribir

Thank you for the unit correction, it is important( it was an embarrrasing mistake ). Let me review, the time( from launch till fall) I get should be divided by two to get the distance: so would I do d=1/2 *a*((t^2)/2) ?

thanks

4. Feb 21, 2006

### forevergone

Yes because the rocket travels in a parabolic shape. The overall time it takes includes both when it rises and falls and since you want the tallest height it flies, you want where time is at half of the overall duration in travel.