Please Help, Another Energy and Momentum

  • Thread starter hybridized
  • Start date
  • #1
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Homework Statement


A construction worker at the top of a ladder drops her 250 g hard hat from a height of 22m. When it reaches the ground it is traveling at 9.0 m/s. What was the average fore of friction as it fell.



Homework Equations


Stuck here....


The Attempt at a Solution


Can't figure out what equations to use.... Tried finding t, then using ft=mv and solving for t, but that does work.
 

Answers and Replies

  • #2
54
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Use the work energy theorem.
 
  • #3
11
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Use the work energy theorem.
Would you mind explaining buddy, kinda lost...
 
  • #4
54
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W = ΔEk + ΔEp

W is work due to friction.
ΔEk is the change in kinetic energy.
ΔEp is the change in gravitational potential energy.

In this case, the hat gains kinetic energy but loses potential energy, so ΔEk is positive, and ΔEp is negative.
 
  • #5
11
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KK I got that, but how would I go on to finding the force of friction?
 
  • #6
54
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W = F x d, you know what d is.
 
  • #7
11
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O I see now, so solving for F would give you the average force. True, thanks buddy mind taking a look at my other thread? Title is Momentum + Energy :)
 

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