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**[SOLVED] Motion in two dimensions question. At wit's end.**

Hi, I'll try to keep this short. I have a Physics exam tomorrow and was doing some textbook questions and can't figure out this one problem. It's killing me! I have the answer (supplied by the back of the book), but just can't seem to get there.

Some help would be much appreciated since I've grown very frustrated with it.

**1. Homework Statement**

The initial speed of a projectile is 80 m/s. If the projectile is to strike a target that is a horizontal distance of 450 m away, what is the minimum time of flight. (Answer 6.1s)

**2. Homework Equations**

Standard laws of motion ignoring air resistance and the like

X(final) = X(initial) + V(initial) (t) + 0.5at^2

**3. The Attempt at a Solution**

I've tried everything I can think of. What's shutting me down every time is that there is no angle supplied so I'm always stuck with two variables I can't eliminate.

Obviously the answer must lie in finding the smallest angle possible for a projectile at 80 m/s to reach 450 meters, I just can't figure out how. I came up with this equation from the formula above, but I have no clue how to use it as my brain is just shutting down at this point (maybe it's useless i don't know, argh!)

450 = 0 +80(cos(alpha))t = 0

t= 5.625/cos(alpha)

If someone could help me get this problem you would earn my undying admiration, and I'll mail you a cookie!

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