Question

A lift is going up. The total mass of the lift and the passenger is $1500kg$. The variation in the speed of the lift is as given in the graph. The tension in the rope pulling the lift at $t={11}^{th}sec$ will be

• A. $12000N$
• B. $14700N$
• C. zero
• D. $17400N$

Answer 1

The correct option is A $12000N$

Find acceleration of lift
At ${11}^{th}$ second lift is moving upward with acceleration which is equal to slope of velocity-time graph at $t=11s$
$a=\frac{0-3.6}{2}=-1.8m/s^2$

Find tension in rope attached to lift
$m=1500kg$
From $FBD$
$T-mg=ma$
$T-1500\left(9.8\right)=1500(-1.8)$
$T=1500(9.8-1.8)$
$=12000N$

Final anwer (c)