Question

In a belt-pulley drive the driving pulley is of 12 cm
diameter and rotates at 360 rpm. Find the rpm of driven
pulley whose diameter is 20 cm.​

Answer 1

Diameter of the driving pulley= 12cm

Speed= 360rpm

Diameter of driven pulley=20cm

Speed, let it be X

Now,

Diameter of driving pulley x Speed of driving pulley = Radius of driven pulley x Speed of driven pulley

=>12 x 360 = 20 x X

$=> \frac{12 \times 360}{20}= X \\\\ X=\frac{12 \times \cancel{360}~18 }{\cancel{20}}= 18 \times 12 = 216 rpm$