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Work done by force.

  • Thread starter rcmango
  • Start date
  • #1
234
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Homework Statement



A 70.0 kg skier rides a 2700 m long lift to the top of a mountain. The lift makes an angle of 14.3° with the horizontal. What is the change in the skier's gravitational potential energy?
in Joules


Homework Equations





The Attempt at a Solution



I can't seem to find why Ef * s = mas
does not work?

i've tried using the equation for an answer and it doesn't seem to give me the right answer.
 

Answers and Replies

  • #2
218
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What is the meaning of the symbols in "Ef * s = mas", especially the *?
 
  • #3
234
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E = "work done by net ext. force

s = displacement

m = mass
a = acceleration
 
  • #4
218
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Thanks :-)

The f and the * ?
 
  • #5
234
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f = force and * = multiplication
 
  • #6
218
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Thanks :-)

* = multiplication, the same as between E and f, m and a, and a and s?

If that's correct then the equation could be rewritten as
Efs = mas
which would be a strange equation because the s is useless; the equation is equivalent to
Ef = ma
and that can't be right because E, work/energy, is force times distance and ma is force so the equation would not be balanced -- the units would not be the same on each side. It would be saying
force x distance x force x distance = force
 

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