Question

A lamp hangs vertically from a cord in a descending elevator that decelerates at 1.4 m/s2. (a) If the tension in the cord is 91 N, what is the lamp's mass

Answer 1

Answer:8.125 kg

Explanation:

Given

deceleration of elevator $a=1.4\ m/s^2$

suppose T is the tension in the cord

therefore net force on lamp is

$F_{net}=T-mg$

$F_{net}=ma$

direction of a and g is in the same direction

$T-mg=m(1.4)$

$T=m(g+a)$

$m=\dfrac{T}{g+a}$

$m=\dfrac{91}{9.8+1.4}$

$m=8.125\ kg$