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Oscillations

Question
CBSEENPH11026358

A pan with a set of weights is attached to a light spring. The period of vertical oscillation is 0.5s. When some additional weights are put in pan, then the period of oscillations increases by 0.1 s. The extension caused by the additional weight is

  • 5.5 cm

  • 3.8 cm

  • 2.7 cm

  • 1.3 cm

Solution

C.

2.7 cm

Given:- T = 0.5 s

We know that,

The time period for oscillation is

            T = 2π mk

k = It is spring constant

m = mass 

⇒          T = 0.5

⇒          0.5 = 2π mk

⇒           14π = mk

On squaring on both sides, we get

⇒            mk = 116 π2                      ....(i)

⇒         T + 0.1 = 2π m + m'k

⇒     0.5 + 0.1 = 2π m + m'k

⇒       0.62π2 = m + m'k 

⇒                  = mk+m'k

⇒         0.624π2 = 116 π2 + m'k                   using eq.(i)

⇒           0.6 24π2 - 116 π2 = m'k 

⇒            m'k = 1.44 - 116 π2

⇒              m'k = 0.4416 π2                          ....(ii)

               m' g = kx

               x = m'kg

⇒                 = 0.4416 π2 × 10

⇒            x = 0.0279

⇒            x = 2.79 × 10-2 m

×            x = 2.7 cm