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cidilon
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Homework Statement
Marian, who is standing on her balcony, is surprised by a pigeon and throws a flowerpot up in the air at 2.1 m/s. It takes 3.0 s for the flowerpot to smash to the ground. The flowerpot experiences acceleration due to gravity of 9.81m/s2 [down].
a) How high is Marian's balcony?
b) How fast was the flowerpot moving just before it smashed to the ground?
v1= 2.1 [up]
a= -9.81m/s2 [up]
t= 3.0 s
Homework Equations
Since acceleration is constant
d = v1*t + .5*a*t*t
v2[squared] = v1[squared] + 2*a*d
The Attempt at a Solution
a)
First i used d = v1*t + .5*a*t*t
d = 2.1*3.0 + .5*-9.81*3.0*3.0
d = -37.8 m [up] or -38 m [up] ---> i round it to 2 sig figs here, right?
Now here is where i get confused.
This is negative displacement because the flower pot is flying most of it's way down to the ground. Right? What i am confused about is, is this the actual displacement from the balcony to the ground? Is Marian's balcony 38 m high?
It just seems not right to me for some reason, it feels like i am missing some sort of step.
If this is the answer, then for b) i use
v2[squared] = v1[squared] + 2*a*d
v2[squared] = 2.1[squared] + 2(-9.81)(-38)
v2[squared] = 749.97[square root]
v2 = 27.4 m/s or 27 m/s --->should i make it three or two figs. I think two figs, right?
If everything is correct so far, why do i have positive velocity instead of negative. Should it not be negative?
Thanks in advance and if i am totally wrong, please do correct me :)
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