Question

A block of mass m = 15 kg is suspended in an elevator with the help of three identical light elastic cords (spring constant k = 100 N/m each) attached vertically. Cord 1 is tied to the ceiling 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 in each of the lower cords is T = 7.5 N. Take g = 10 $m/s^2$. If now the elevator starts moving with given four accelerations shown in column I and Column II gives the displacement of the block with respect to elevator when it is accelerating. Column III gives tension in the cord 1 when elevator is accelerating.

Column III represents the tension in chord 1.

• A. (I)(i)(S)
• B. (II)(i)(R)
• C. (III)(ii)(P)
• D. (IV)(iii)(Q)

Answer 1

The correct option is B

(II)(i)(R)

For elevator acceleration 1.5 $m/s^2$, tension in cord 2 and cord 3 is zero

So, $T_1-150=\left(15\right)\left(1.5\right)$

$\Rightarrow$ Tension in cord 1, $T_1=172.5$ N