Question

A Disc mounted on the shaft of a machine has 12 pattern points. The number of flashes projected on the disc by a stroboscope is 3000 in a minute. If the Disc appears stationary and has single image of 12 points then the speed of the machine is _____ $rpm.$

• A. 250

Answer 1

The correct option is A 250
$\text{Speed of machine when pattern appear stationary}$

$n=\frac{f}{m}=\frac{3000}{12}=250rpm$