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falconpunch
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Homework Statement
A 45.0 kg child is in a swing that is attached
to ropes 1.90 m long.
The acceleration of gravity is 9.81 m/s2 .
Find the gravitational potential energy as-
sociated with the child relative to the child’s
lowest position under the following condi-
tions:
a) when the ropes are horizontal.
Answer in units of J.
Homework Equations
Height of a pendulum:
h=L(1-cos(θ))
Potential Energy
PE=mgh
The Attempt at a Solution
So first I found the height of the swing at a horizontal position which I assumed is as at 90°.
h=L(1-cos(θ))
2.75m=1.9(1-cos(90))
Then I used that height and put it into the formula for potential energy
PE=mgh
1213.99 J? = (45)(9.81)(2.75)
but the online homework interface I have to use to input my answer tells me this isn't correct. I was wondering if maybe my answer isn't in Joules, do I need to convert something. Any help would be greatly appreciated.
I realized my problem, i had my calculator in radian's sorry for the stupid question, I'd delete the question if i can find out how
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