Question

A punching press punches 30 holes per min in a plate requiring 12 kJ of energy per hole during each cycle. Actual punching takes 30% of the cycle time. A flywheel connected to the machine electric motor. The flywheel rotates at a mean speed of 240 rpm and the fluctuation of speed is not to exceed $\pm$ 2 percent of the mean speed
The moment of inertia of the fly wheel lo be used is

• A. $333kg-m^2$
• B. $222kg-m^2$
• C. $444kg-m^2$
• D. $123kg-m^2$

Answer 1

The correct option is A $333kg-m^2$

Actual Punching time = 30% of cycle time

$=0.3\times 2=0.6sec$

$\Delta E=6\times (2-0.6)=8.4kJ$

$\Delta E=I{\omega }_{mean}^2{C}_s$

$\Rightarrow 8400=I\times (8\pi {)}^2\times 0.04$

$\Rightarrow I=332.46kg-m^2$