- #1
Daniiel
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Homework Statement
[PLAIN]http://img690.imageshack.us/img690/5756/12281060.jpg
Homework Equations
k = 0.5 mv^2
projectile motion
The Attempt at a Solution
Ok so for part one i just did some algebra and got 1:1 as the ratio, no problems there
For part two i treated it as a projectile after it leaves the roof with v = root (2g)
with that i used y = v sin theta t - 0.5gt^2
to find t
so -3 = root (19.6) sin240 - 4.9 t^2
root (19.6) sin240 = -3.834
simplified and changed to a quadratic 4.9t^2 + 3.834t - 3 = 0
found t with the quadratic formula, t= 0.4836
then subbed into Vy = V sin theta - gt
find Vy = -8.57
So that's the velocity of the y component
Do i have to add that to the velocity of the y component of the initial velocity?
because I've tried it both ways, I'm a bit confused, my tutor told me to add both the inital and final y components, but he didnt treat it as projectile motion, he did it a different way
But let's just say 8.57 is Vy
Vx = v sin 60 = 3.834
the velocity = the magnitude of 3.834i + 8.57j = 9.39
then K = .5 * 5 * 9.39^2 = 220.43
Kinetic rotational energy = 5g
so 220.43/ 5g = 4.5
so the ration is 4.5:1 ?
when i find the ratio by adding the inital Vy and the final Vy i get 6.7:1 or somthing like that
is this right?
my tutor for 7.04:1, but i noticed afew errors so I am not sure if its correct, it's sure a cleaner answer than 4.5 though
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