অভিকর্ষ বল দ্বারা কৃতকাজ

A particle tied to a string describes a vertical circular motion of radius r continually. If it has a velocity 3gr\sqrt{3gr} at the highest point, then the ratio of the respective tensions in the string holding it at the highest and lowest points is

হানি নাটস

Tension at highest point

TH=mv2rmg=3mgmg=2mgT_H=\dfrac{mv^2}{r}-mg=3mg-mg=2mg

and tension at lowest point

TL=mv2r+mgT_L=\dfrac{mv^2}{r}+mg

Here, VL2=3gr+2g.2r=7grV^2_L=3gr+2g.2r=7gr

So, TL=7mg+mg=8mgT_L=7mg+mg=8mg

Hence, THTL=2mg8mg=14\dfrac{T_H}{T_L}=\dfrac{2mg}{8mg}=\dfrac{1}{4}

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