Ask Your Teacher A 51-kg pole vaulter running at 11 m/s vaults over the bar. Her speed when she is above the bar is 1.1 m/s. Neglect air res

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Ask Your Teacher A 51-kg pole vaulter running at 11 m/s vaults over the bar. Her speed when she is above the bar is 1.1 m/s. Neglect air resistance, as well as any energy absorbed by the pole, and determine her altitude as she crosses the bar.

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Thu Thảo 6 months 2021-08-17T11:52:45+00:00 1 Answers 0 views 0

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  1. Jezebel
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    2021-08-17T11:54:40+00:00
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    Answer:

    6.11 N

    Explanation:

    Let,

    m= mass of vaulter

    Vi initial speed =11 m/s

    Vf speed on pole (final) =1.1 m/s

    Yi = initial height (when on ground)=o m

    Yf = Height while crossing the pole =?

    This problem can be solved by using conservation of energy rule;

    KEi + PEi = KEf + PEf

    ==> 1/2 mVi^{2}+ mg Yi_{} = 1/2 m Vf^{2}+mgYf_{}

    Initially the altitude of vaulter is zero i-e Yi=0_{} ==> PEi = mg Yi_{}= mg×0=0

    ==>1/2 mVi^{2}= /2 m Vf^{2}+mgYf_{}

    ==> mVi^{2}=m Vf^{2}+2mgYf_{}

    cancelling m

    ==> Vi^{2}= Vf^{2}+2gYf_{}

    ==> Vi^{2}– Vf^{2}=2gYf_{}

    ==> Yf_{}=\frac{Vi^{2}-Vf^{2} }{2g}

    ==> = =\frac{11^{2 }-1.1^{2} }{2 (9.8)}

    ==>  Yf_{}==\frac{119.79}{19.6}=6.11N

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