Total tension in cable of the elevator:
An elevator having weight 5000N is ascending with an acceleration of 3m/sec2. During this ascent its operator which is having weight 700N is standing on the scale placed on floor. What is scale reading? What will be total tension in cable of the elevator during this motion?
Sol: Given, WE = 5000N, a = 3m/sec2, WO = 700N,
Let R = Reaction offered by the floor on operator. This is equal to the reading of scale.
T = total tension in cable
Net upward force on operator
= R eaction offered by the floor on operator - Weight of operator
= R - 700
Net force = ma
R - 700 = (700/9.81)X 3
R = 914.28N .......ANS
Now for finding total tension in cable, Total weight of elevator is considered.
Net upward force on the elevator and operator
= Total tension in cable - Total weight of elevator and operator
= T - 5700
But net force = mass X acceleration
T - 5700 = (5700/9.81) X 3
T = 7445N .......ANS