Question

steel wire of 8 mm diameter is used for lifting a load of 1200 N at its lower end, the

length of the wire being 150000 mm. Calculate the total elongation of the wire ______ mm.

(Assume E = 2 x 105 N/mm2

, unit weight of steel = 8 x 10-5 N/mm3

)​

Answer 1

Explanation:

Forces at the lowest point are gravitational force and centrifugal force

F=mg+mω 2

r=mg+mω 2 L

Δl= YAFL = Y×πr 2

(mg+mω 2 L)L

ω=2πf=2π×2=4π

Δl= 2×10 11 ×π×(10 −3 )2(30+3×16π2 ×1.5)×1.5 =1.77×10 −3m