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A block of mass `m` is attached with a massless spring of force constant `k`. The block is placed over a fixed rought inclined surface for which the coefficient of friction is `mu=(3)/(4)` . The block of mass `m` is initially at rest . The block is mass `M` is released from rest with spring in unstretched state. The minimum value of `M` required to move the block up the plane is `(` neglect mass of string and pulley and friction in pulley `)` A. `(3)/(5)m`B. `(4)/(5)m`C. `(6)/(5)m`D. `(3)/(2)m` |
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Answer» Correct Answer - A As long as the block of mass `m` remains stationary, the block of mass `M` released from rest comes down by `(2Mg)/(K)(` before coming it rest momentanly again `)` . Thus the maximum extension in spring is `x=(2Mg)/(K) …….(1)` for block of mass `m` to just move up the incline `kx=mg sin theta + mu mg cos theta ........(2)` `2Mg=mgxx(3)/(5)+(3)/(4) mg xx(4)/(5)` or `M=(3)/(5) m Ans. ` |
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