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5.work,energy,power and collision — Physics STD 11 Science — Question

Rajasthan BoardEnglish MediumSTD 11 SciencePhysics5.work,energy,power and collision1 Mark
MCQ
A block of mass $m$ is suspended by a light thread from an elevator. The elevator is accelerating upward with uniform acceleration $a$ . The work done by tension on the block during $t$ seconds is $(u = 0)$
  • ✓
    $\frac{m}{2}\left( {g + a} \right)a{t^2}$
  • B
    $\frac{m}{2}\left( {g - a} \right)a{t^2}$
  • C
    $\frac{m}{2}g\,a{t^2}$
  • D
    $0$
✓

Answer

Correct option: A.
$\frac{m}{2}\left( {g + a} \right)a{t^2}$
a
$\mathrm{T}=\mathrm{mg}+\mathrm{ma}, \quad \mathrm{S}=\frac{1}{2} \mathrm{at}^{2}$

$\mathrm{W}_{\mathrm{T}}=\mathrm{T} \times \mathrm{S}$

$=\frac{\mathrm{m}(\mathrm{g}+\mathrm{a}) \mathrm{at}^{2}}{2}$

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