1.

The following figure shows a block of mass m suspended from a fixed point by means of a vertical spring. The block is oscillatting simple harmonically and carries a charge q. There also exists a uniform electric field in the region. Consider four different cases. The electric field is zero in case 1, mg//q downward in case 2, mg//q upward in case 3, and 2mg//q downward in case 4. The speed at mean position is same in all cases. Select the correct alternative (s).

Answer»

Time PERIODS of OSCILLATION are equal in case 1 and case 3.
AMPLITUDES of displacement are same in case 2 and case 3.
The maximum elongation (increment in length from natural length) is maximum in case 4.
Time periods of oscillation are equal in case 2 and case 4.

SOLUTION :a.,b.,c.,d.
(a) Only equilibrium position changes. Time period remains same `T=2pisqrt(m//K)`.
(b) `(1)/(2)kx^(2)=(1)/(2)mv^(2)`
So `v` at mean position is same amplitude will be same.
(c) In case `4` equilibrium psotion is `x_(0)=3mg//k`.


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