Correct Answer - Option 1 : 708.14 rev/min
Concept:
G-factor is the ratio of centrifugal force to weight:
\(G =\frac{F_c}{mg} = \frac{mr\omega^2}{mg}\)
Calculation:
Given:
G-factor = 70, do = 25 cm = 0.25 m, g = 10 m/s2
\(G =\frac{F_c}{mg} = \frac{mr\omega^2}{mg}\)
For horizontal centrifugal casting, the outer radius is considered during the calculation.
\(G = \frac{mr\omega^2}{mg} = \frac{d_o}{2g}\left ( \frac{2\pi N}{60}\right )^2=70\)
N = \(\sqrt{\frac{2\times70\times10}{0.25}}\times\frac{60}{2\pi}\)
N = 714.60 \(\approx\) 708.14 rpm