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Energy and motion problem

  • Thread starter sonic91
  • Start date
  • #1
9
0

Homework Statement


Betty weighs 427 N and she is sitting on
a playground swing seat that hangs 0.22 m
above the ground. Tom pulls the swing back
and releases it when the seat is 0.88 m above
the ground.
The acceleration of gravity is 9.8 m/s2 .
How fast is Betty moving when the swing
passes through its lowest position?
Answer in units of m/s.


Homework Equations


KE=1/2 M V^2
PEg=Mgh
i might be missing an equation here


The Attempt at a Solution


i was thinking that potential energy gravitational would turn into Kinetic energy then i solved for v.

PEg= 427 newtons*.66 i used the change in height for h and got 281.82 Joules for my answer. then i said that should transfer to KE.

281.82 joules= 1/2* 427/9.8 Kg * V^2 and i got 11.3737 m/s as my answer. when i checked this it turned out to be wrong. i think i may have to apply circular motion concepts to this problem, but i'm not quite sure how to do that.

thanks in advance.
 
Last edited:

Answers and Replies

  • #2
10
0
Your logic looks sound; it must just be a math error throwing you off... If the work you have here is what you typed into your calculator, then I have two suggestions: first, the weight in the 2nd equation should be 427, not 527... secondly, did you take the square root of both sides at the end? Other than that, I don't know what to tell you.
 
  • #3
9
0
yeah i've got it figured out now thanks.
 

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