Question

A 100 kg elevator is descending with an acceleration od 1.0 ms-2. Calculate the tension in the suspending cable.

Answer 1

Let's choose the upwards as the positive direction and apply the Newton's Second Law of Motion:

$$T - mg = -ma,$$ $$T = mg - ma = m(g - a),$$ $$T = 100 \ kg \cdot (10 \ \dfrac{m}{s^2} - 1.0 \ \dfrac{m}{s^2}) = 900 \ N.$$

Answer:

$T = 900 \ N.$