It is hard for me to type the nasty formula, but i will try.
Suppose you are pulling with a force F with an angle q (measured from horizontal). The the normal force N (or the supporting force from the surface) should be:
N = mg - F*sinq
Thus the friction force f is given by
f = N*mk = (mg - F*sinq)*mk
And if the object is moving with a constant speed, the force pulling forward ( F*cosq ) should be equal to the force pulling backward (the friction). Therefore
F*cosq=(mg - F*sinq)*mk
Solving for F, we have
F = mg*mk/(mk*sinq + cosq)
To find the minimum of F, we calculate
dF/dq = mg*mk*(mk*cosq - sinq)/(mk*sigq +cosq)^2
and let dF/dq=0, we have
(mk*cosq - sinq) = 0
This gives
tanq = mk
回複:Can you show your work? Thank!
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Thank you so much !! If I did not learn Calculus,how could I sol
-pingshi-
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10/02/2009 postreply
00:48:46
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回複:Thank you so much !! If I did not learn Calculus,how could I
-oldbookworm-
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10/02/2009 postreply
21:47:15
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Thanks! I get your idea.
-pingshi-
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10/02/2009 postreply
23:54:18