Question

A shaft rotating initially at 1725 RPM is brought to rest in 20 second calculate the number of revolutions made by shaft before stopping

Answer 1

The number of revolutions made by the disc is found by using the equations of angular motion. The equation that I pick to find the number of revolutions is

$\Delta \Theta =\frac{1}{2}(w_0+w)t.$

where $\Delta \Theta$ is the number of revolutions made, $w_0=1725RPM$ and $w=0$ and $t$ is the time it takes to make the change in angular speed.

From the given values, we get that

$\Delta \Theta =\frac{1}{2}(w_0+w)t= \frac{1}{2}\times 1725RPM\times \frac{20}{60}M =287.5Rev$

The shaft makes 287.5 revolutions.