InterviewSolution
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InterviewSolution
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Two masses `m_(1)` and `m_(2)` concute a high spring of natural length `l_(0)` is compressed completely and tied by a string. This system while conving with a velocity `v_(0)` along `+ve` x-axis pass thorugh the origin at `t = 0`, at this position the string sanps, Position of mass `m_(1)` at time t is given by the equation `x_(1)t = v_(0)(A//1-cosomegat)`. Calculate (i) position of the particle `m_(2)` as a funcation of time, (ii) `l_(0)` in terms of A. |
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Answer» Correct Answer - (i) `v_(0)t + A(m_(1))/(m_(2))(1-cosomegat)` , (ii) `((m_(1))/(m_(2)) + 1) A` (i) Two massse `m_(1)` and `m_(2)` are connected by a spring of length `l_(0)`. The spring is in compressed position. It is held in this position by a string. When the string snaps, the spring force is brought into operation. The spring force is an internal force w.r.t masses-spring system. No external force is applied on the system. The velocity of centre of mass will not change. Velocity of centre of mass `= v_(0)` `:.` Location/x -coordinate of centre of mass of time `t = v_(0)t` `:. barv = (m_(1)x_(1) + m_(2)x_(2))/(m_(1) + m_(2))` `rArr v_(0)t = (m_(1)[v_(0)t - A(1-cosomegat)]+m_(2)x_(2))/(m_(1) + m_(2))` `rArr (m_(1)+m_(2))v_(0)t=m_(1)[v_(0)t-A(1-cosomegat)]+m_(2)x_(2))` `rArr m_(1)v_(0)t + m_(2)v_(0)t = m_(1)v_(.0)t - m_(1)A(1-cosomegat)] + m_(2)x_(2)` `rArr m_(2)x_(2) = m_(2)v_(0)t + m_(1)A(1-cosomegat)` `rArr x_(2)=v_(0)t + (m_(1)A)/(m_(2))(1-cosomegat)"......"(i)` To express `l_(0)` in terms of A. `:. x_(1) = v_(0)t - A(1-cosomegat) :. (dx_(1))/(dt^(2)) = -Aomega^(2) sinomegat` `:. (d^(2)x^(2))/(dt^(2)) = - Aomega^(2) cosomegat "........"(ii)` `x_(1)` is displacement of `m_(1)` at time t. `:. (d^(2)x_(1))/(dt^(2)) =` acceleration of `m_(1)` at time t. When the spring attains its natural length `l_(0)`, then acceleration is zero and `(x_(2) - x_(1)) = l_(0))` `:. x_(2) x_(1) = l_(0)` , Put `x_(2)` from (i) `rArr [v_(0)t + (m_(1)A)/(m_(2)) (1-cosomegat)] - [v_(0)t - A(1-cosomegat)] = l_(0)` `rArr l_(0) = ((m_(1))/(m_(2)) + 1)A(1-cosomegat)` When `(d^(2)x_(1))/(dt^(2)) = 0, cosomegat = 0` from (ii). `:. l_(0) = ((m_(1))/(m_(2)) + 1)A`. |
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