[iogames]

Originally Posted by Opserty

In Kinematics initial doesn't always refer to the very start, you can take the initial velocity of an object when its already moving and use that as your starting point.

Anyhoo...with regards to your problem I think you have to make a point of the horizontal component being independent of the vertical component. The object will travel in a parabola.

Vertically speaking:
Displacement = 0 (Your going up then coming back down)
Initial velocity = Vertical component of Initial velocity. ( u sin60)
Acceleration = Acceleration due to gravity [-9.8 (+ve or -ve depending on your frame of reference)]
Time = Unknown
[S]Final Velocity = Not interested[/S]

Horizontally:
Displacement = 15 miles (Quite why your still working with imperial units I don't know :erm
Initial velocity = Horizontal component of Initial velocity. ( u cos60 = 0.5u)
Acceleration = 0 (Assuming there is no air resistance)
Time = Unknown
[S]Final Velocity = Not interested[/S]

Then for both I used this equation:


Solve it for Horizontal first, that will give you a value of t in terms of u. Substitute this into the same equation for the vertical motion and it will give you the Initial Horizontal Velocity.

Don't forget to calculate the Initial Velocity from its Horizontal component, (basically its u/cos60)

That is how I would tackle it anyway, bearing in mind I haven't done any kind of projectile motion, so there may be an easier way to do it.

Good luck

I concur!