<p>This question doesn't seem that hard...but for some reason I just can't figure it out...plz any help would be appreciated. </p>
<p>A cannon is placed on top of a mountain (of unknown height above the ground). The cannon shoots a cannonball, 4.5kg, which lands 215m from the base of the mountain. With what speed, in m/s, is the cannonball initially shot from the cannon?</p>
<p>can we assume that the cannon is being fired parallel to the x axis?</p>
<p>yes</p>
<p>sorry for not including that with the problem...the problem itself is a diagram, that paragraph is just me trying to explain it in words</p>
<p>ok gotcha.... i'm working on it</p>
<p>If we don't know the force of the cannonblast, or the height of the mountain, or the angle the cannonball was shot at, one can't tell. We need two of those three things. Wait, if we don't know the angle, then we need force AND height.</p>
<p>thanks JeNeSaisQuoi, you rock :)</p>
<p>Wow, the last sentence of my last post was really stupid.</p>
<p>no, we just need to figure out how long it was in the air for... y direction does not affect X direction pull since it was shot parallel to the x axis</p>
<p>tomas: well, we have the angle. the cannon is fired parallel to the x-axis. we don't have any of the others though.</p>
<p>maybe this problem can't be done?</p>
<p>it doesn't give you a time?</p>
<p>unfortunately not</p>
<p>damn......</p>
<p>I could be symbolically, if that's what's intended. Using basic kinematics, it should be...</p>
<p>do they want you to solve it using variables in your answer?</p>
<p>no, i think it's asking for a number.</p>
<p>i did get an answer in terms of y though - not sure if it's right, i kinda did it hurriedly and plus it's 1:20 AM here - </p>
<p>sqrt(226733.63/y) = v</p>
<p>wow, i don't want to do this right now; I'm clearly a slave to the solve function on my 89</p>
<p>heh...i did that one caveman-style. aka, pencil, paper, TI83+. haha.</p>
<p>if you dont wanna do it, thats cool, thanks anyway</p>
<p>what equation did you use?</p>
<p>all of the retarded ones i'm looking at involve acceleration or time or both or velocity... criminy</p>
<p>Can we use energy, even though we know nothing about the initial speed? I can't see how you solved only in terms of y</p>
<p>tomas: yeah, we can use energy. dunno if it'll help though.</p>
<p>ok i'll do my best to type this out...and i'm pretty sure i did this wrong, but anyways...</p>
<p>x = vt ---> 215 = vt ---> 215/v = t</p>
<p>y = vt + .5at^2</p>
<p>v = 0 m/s (in the y direction); y = .5at^2; substitute for t
a = 9.81 m/s^2</p>
<p>(.5)(9.81)(215^2/v^2) = y</p>
<p>then just solve for v in terms of y...but really it doesn't help much...</p>