1.

A block of mass m=15g is suspended in an elevator with the help of three identical light elastic cords (spring constant k=100N//m each) attached vertically. One of them cord 1 is tied to the ceilling of the elevator and the other two cords 2 and 3 are tied to the elevator floor as shown in the figure. When the elevator is stationary the tension force is each of the lower cords is T=7.5N. Take g=10m//s^(2). Now the elevator starts moving with given four accelerations shown in column I. Column II given the displacement ofthe block with respect to elevator when its is accelerating. Column III gives tension in the cords when elevator is accelerating. Tension in cord -2

Answer»

(I)(iv)(P)
(II)(i)(Q)
(III)(iii)`(R)`
(IV)(ii)(S)

SOLUTION :For ELEVATOR acceleration `1m//s^(2)`, tension in cord 2 and cord 3 decreases.
So `165+DeltaT-2xx(7.5-DeltaT)-150=(15)(1)`
`implies DeltaT=5N`
`implies` Tension in cord 2, `T_(2)=2.5N`


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