Question

The total mass of an elevator, with an $80kg$ man in it, is $1000kg$. It is brought to rest from $8m/s$ over a distance of $16m$. During retardation, the tension in the supporting cable and the force exerted by the man on the floor are respectively (g $={10ms}^{-2}$)

• A. 4000 N, 640 N
• B. 8000 N, 640 N
• C. 4000 N, 320 N
• D. 8000 N, 320 N

Answer 1

The correct option is B 8000 N, 640 N

Acceleration $a$ of the elevator is given by $v^2-u^2=2asor0-8^2=2a\left(16\right)ora=-2m/s^2$
Let $M$ be the total mass of the elevator then, $T-Mg=Ma$
Tension $T=M(g+a)=1000(10-2)=8000N$
Force exerted on floor by man $=80(g+a)=80(10-2)=640N$