Question

A block of mass m is suspended by a light thread from an elevator.The elevator is accelerating upward with uniform acceleration a. The work done by tension on the block during t seconds is (1 = 0) :

• A. $\frac{m}{2}(g+a)a{t}^2$
• B. $\frac{m}{2}(g-a)a{t}^2$
• C. $\frac{m}{2}ga{t}^2$
• D. 0

Answer 1

The correct option is A $\frac{m}{2}(g+a)a{t}^2$

T acting on string due to mass= +mg
T acting on string due to upward accelration= +ma
Total T= m(g+a)
$S=ut+0.5a{t}^2=0.5a{t}^2$
$W=\left(0.5a{t}^2\right)\left(m\right(g+a\left)\right)$
$W=\frac{m(g+a)a{t}^2}{2}$