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NTA Abhyas 2020
Exam
NTA Abhyas
Year
2020
Subject
Physics
Chapter
Mechanical Properties of Solids

NTA Abhyas 2020 · Physics · Mechanical Properties of Solids

One end of a long metallic wire of length L is tied to the ceiling....

One end of a long metallic wire of length LL is tied to the ceiling. The other end is tied to a massless spring of spring constant kk. A mass mm hangs freely from the free end of the spring. The area of cross-section and Young’s modulus of the wire are AA and YY respectively. If the mass is slightly pulled down and released, it will oscillate with a time period TT equal to&One end of a long metallic wire of length L is tied to the ceiling. The other end is tied to a massless spring of

Options

  1. A2π(mk)1/22\pi\left(\dfrac{m}{k}\right)^{1} / 2
    &
  2. B2\pi\sqrt{\dfrac{m\left(YA + kL\right)}{YAk}}
  3. C2\pi \left[ \left(\dfrac{mYA}{kL}\right)12\dfrac{1}{2}\right]
    &
  4. D2π[(mLYA)12]2\pi \left[ \left(\dfrac{mL}{YA}\right)\dfrac{1}{2}\right]

Correct answer

B. 2\pi\sqrt{\dfrac{m\left(YA + kL\right)}{YAk}}

Step-by-step solution

Equivalent force constant for a wire is given by k=YALk = \dfrac{YA}{L}. Because in case of a wire, F=YAL∆LF = \dfrac{YA}{L} ∆ L and in case of spring, F=k∆xF = k ∆ x. Comparing these two, we find k of wire =YAL= \dfrac{YA}{L}

keq=k1k2k1+k2=YALkYAL+k=YAkYA+Lk{k}_{eq} = \dfrac{{k}_{1}{k}_{2}}{{k}_{1} + {k}_{2}} = \dfrac{\dfrac{YA}{L}k}{\dfrac{YA}{L} + k} = \dfrac{YAk}{YA + Lk}

One end of a long metallic wire of length L is tied to the ceiling. The other end is tied to a massless spring of

∴T=2πmkeq=2πm(YA+Lk)YAk∴ T = 2\pi\sqrt{\dfrac{m}{k\text{eq}}} = 2\pi\sqrt{\dfrac{m\left(YA + Lk\right)}{YAk}}
&

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