- #1
patterson
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Homework Statement
I need to be able to get a equation to figure out the initial speed as an object leaves the origin, and I don't understand what exactly I am suppose to treat these as? Basically they are showing us vectors, Vo being velocity vector, and Vox and Voy being x and y components of that vector. If I am given a problem where I am given no Vox or Voy or Vo, and nothing else but what is given (acceleration is constant for y= -g and Ax=0) and distance from origin = 12.6m from apex of trajectory, how do I go about solving for Vox and Vot seeing that the book says I have to have Vo(Cos(Θo) = Vox and Vo(Sin(Θo) = Voy I am misunderstanding this because they say they are velocity, and i thought velocity is measured in m/s or ft/s as a speed, not a distance.
If I am only given a distance from the mid point (12.6m) and an apparent trajectory angle of 3 degrees, at what speed must the object leave its origin to rise .33m at its apex?
I am unsure what to do next because when I calculate the VoSinVo(Cos(Θo) = Vox and Vo(Sin(Θo) = Voy I have .66m for Voy and 12.617 for Vo and this is obviously not right
How the heck am I suppose to pull speed from this anyways I just don't get this crap I've worked 10 hours on this and I just don't get it
Homework Equations
Vo(Cos(Θo) = Vox and Vo(Sin(Θo) = Voy
Vx=Voxt + Ax(squared)
∆x = Voxt + 1/2 axt(squared)
Vx(squared) = Voxt(squared) + 2ax∆x
Vy=Voy + Ayt
∆y = Voyt + 1/2 Ayt(squared)
Vy(squared) = Voy2 + 2ay∆y
The Attempt at a Solution
it is sad very very sad
where do I begin to explain what I am doing here I have Vox= VoCos(theta) and Voy=VoSin(theta)
12.6m Sin (3degrees) = .66 = Voyt
Asquared + bsquared = Csquared
.66(squared) + 12.6m(squared) = C = 12.617m/s
so Vo= 12.617m/s
∆x = Voxt = 25.2m = 12.6m(t)
t= 2 seconds
∆y = y=yo = Voyt - 1/2gt(squared)
.66m = .66m/s (t) - (4.9m/s(squared)t(squared)
Vx = Vox = VoCos(theta) = 12.6m/s
Vy = VoSin (theta) - gt
12.617 sin (3degrees) - (9.8m/s(squared))(2seconds) = - 18.94 m/s
see what I mean this book sucks the teacher helps out nothing but more confusion, no clarification. I am going to blow up soon and i just need more understanding how this stuff is even suppose to flow together, they give me no formulas to work with I try to use their formulas and look what I come up with nothing but stuff that is wrong all the way through apparently according to the book which tlels me it is 48.6 m/s
how the heck do they come up with that I have -18.94m/s
i mean seriosuly if they are going to put questions like this in here why do they not even tell us how to even go about getting a velocity from nothing but x and y and a degree i mean speed from that i don't get it someone please help before I off myself.