I am doing a projectile motion problem with my own results, and the unknown's of initial velocity and time. It is at 0 degrees, which I thought would mean I could find the vertical down of the projectile (where at an angle you find the vertical up and down because it goes up first). I have tried multiple ways but I am not sure if what I am doing is right.(adsbygoogle = window.adsbygoogle || []).push({});

The foam bullet is launched from a height of 1.266metres and travels a length of 6.55metres at 0°.

∴Vertical Down

Acceleration due to gravity (a) = -9.8m/s

Final velocity (v) = 0

Initial velocity (u) = ?

Time taken (t) = ?

Displacement down (s) = 1.266

Therefore I decided to use the motion equation (v^2)=(u^2)+2as

And when calculated results in u equalling 4.98m/s

And therefore distance/speed=t

6.55/4.98=1.32seconds

However, my problem when I get to this stage is that other foam bullets of slightly different weight etc have completely different distances, therefore different times, but with this calculation apparently the same velocity.

So my problem is I do not know whether I am on the right track or not, or have completely messed it up. Thankyou in advanced for your help!

**Physics Forums | Science Articles, Homework Help, Discussion**

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Homework Help: Finding initial velocity for projectile motion at 0 degrees

**Physics Forums | Science Articles, Homework Help, Discussion**