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JEE Main 2007
Exam
JEE Main
Year
2007
Subject
Physics
Chapter
Laws of Motion

JEE Main 2007 · Physics · Laws of Motion

A body weighing 13 ~kg is suspended by two strings 5 ~m and 12 ~m...

A body weighing 13 kg13 \mathrm{~kg} is suspended by two strings 5 m5 \mathrm{~m} and 12 m12 \mathrm{~m} long, their other ends being fastened to the extremities of a rod 13 m13 \mathrm{~m} long. If the rod be so held that the body hangs immediately below the middle point. The tensions in the strings areA body weighing 13 ~kg is suspended by two strings 5 ~m and 12 ~m long, their other ends being fastened to the

Options

  1. A12 kg12 \mathrm{~kg} and 13 kg13 \mathrm{~kg}
  2. B5 kg5 \mathrm{~kg} and 5 kg5 \mathrm{~kg}
  3. C5 kg5 \mathrm{~kg} and 12 kg12 \mathrm{~kg}
  4. D5 kg5 \mathrm{~kg} and 13 kg13 \mathrm{~kg}

Correct answer

C. 5 kg5 \mathrm{~kg} and 12 kg12 \mathrm{~kg}

Step-by-step solution

T2cos⁡(π2−θ)=T1cos⁡θ⇒T1cos⁡θ=T2sin⁡θ\mathrm{T}_2 \cos \left(\frac{\pi}{2}-\theta\right)=\mathrm{T}_1 \cos \theta \Rightarrow \mathrm{T}_1 \cos \theta=\mathrm{T}_2 \sin \theta T1sin⁡θ+T2cos⁡θ=13\mathrm{T}_1 \sin \theta+\mathrm{T}_2 \cos \theta=13. ∵\because\mathrm{OC}=\mathrm{CA}=CB=\mathrm{CB} ⇒∠AOC=∠OAC\Rightarrow \angle \mathrm{AOC}=\angle \mathrm{OAC} and ∠COB=∠OBC\angle \mathrm{COB}=\angle \mathrm{OBC} ∴sin⁡θ=sin⁡A=513\therefore \sin \theta=\sin \mathrm{A}=\frac{5}{13} and cos⁡θ=1213\cos \theta=\frac{12}{13} ⇒T1 T2=512⇒T1=512 T2\Rightarrow \frac{\mathrm{T}_1}{\mathrm{~T}_2}=\frac{5}{12} \Rightarrow \mathrm{T}_1=\frac{5}{12} \mathrm{~T}_2  T2(512⋅513+1213)=13\mathrm{~T}_2\left(\frac{5}{12} \cdot \frac{5}{13}+\frac{12}{13}\right)=13  T2(16912⋅13)=13\mathrm{~T}_2\left(\frac{169}{12 \cdot 13}\right)=13  T2=12 kgs.⇒T1=5 kgs\mathrm{~T}_2=12 \mathrm{~kgs} . \Rightarrow \mathrm{T}_1=5 \mathrm{~kgs}. A body weighing 13 ~kg is suspended by two strings 5 ~m and 12 ~m long, their other ends being fastened to the
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