Question

a lift of mass 1000kg & its max. accl^n is 1.2m/sec^2 & amax. safe stress is 1.4*10^10n/m^2.find the maximum dimeter of the wire??

Answer 1

mass of lift  =1000 kg
maximum acceleration = 1.2 m/s²
when the lift goes upward, the maximum downward force = ma
where a = g+1.2 = 9.8+1.2 = 11 m/s²

maximum tension = 1000×11 = 11000 N
safe stress = 1.4×10¹⁰ N/m²

Stress = Force/area 
⇒1.4×10^10 = 11000/A
⇒A = 11000/1.4×10^10 = 7.857×10^-7 m² 
⇒ πr² = 7.857×10^-7
⇒ r = √7.857×10^-7/π = 0.0005 m = 0.05cm

diameter = 0.05×2 = 0.1 cm = 1mm
The minimum diameter of the wire should be 1mm. There is no maximum.