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posted by  zara1 on 7/3/2008 5:07:40 PM  |  status: Live  

physics algebra base

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Question Details:
A runner traverses a 55 m long stretch on a horizontal track in 12 s at a fairly constant speed. All the while she experiences a retarding force of 1.0 N due to air friction. What power was developed in overcoming that friction?
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posted by zsm28 on 7/3/2008 5:16:26 PM  |  status: Live
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zara1's comment:
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Response Details:
note the constant speed, the active force = 1.0 N
the power = force times speed = 1.0 N * 55 m/12 s = 4.6 W
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posted by Altair on 7/3/2008 5:20:58 PM  |  status: Live
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zara1's comment:
"thanks"
Response Details:
assume she's force to overcome the air resistance is: F
 
then F-1.0 N = ma = 0 since her speed is constant so a = 0
 
F=1.0N
 
the work is done by her is: w = F*55m  = 55J
 
and the power is: P = w/Δt = 55J / 12s = 4.583 W
 
 

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