Question

The wire feed controls the amperage during the welding process. A control knob labeled in metric units shows a maximum wire-feed speed of 350 mm/sec. What is the maximum speed in inches per minute? (Round to two significant digits.)

Answer 1

Consider that the maximum wire-feed speed is 350 mm/sec,

$S_{\max }=350\text{ }\frac{\operatorname{mm}}{\sec }$

Its is asked to convert the expression into inches per minute.

Consider the following conversions,

$\begin{gathered} 1\text{ mm}=\frac{1}{25.4}\text{ inch} \\ 1\text{ sec}=\frac{1}{60}\text{ min} \end{gathered}$

Then, it follows that,

$\begin{gathered} 1\text{ }\frac{\operatorname{mm}}{\sec }=\frac{(\frac{1}{25.4})\text{ inch}}{(\frac{1}{60})\text{ min}} \\ 1\text{ }\frac{\operatorname{mm}}{\sec}=\frac{1}{25.4}\times\frac{60}{1}\frac{\text{ inch}}{\text{ min}} \\ 1\text{ }\frac{\operatorname{mm}}{\sec}\approx2.3622\frac{\text{ inch}}{\text{ min}} \end{gathered}$

Substitute this conversion of units in the expression for speed,

$\begin{gathered} S_{\max }=350\text{ }\frac{\operatorname{mm}}{\sec } \\ S_{\max }=350\text{ }\cdot\text{(1 }\frac{\operatorname{mm}}{\sec}) \\ S_{\max }=350\cdot(2.3622\text{ }\frac{\text{ inch}}{\min }) \\ S_{\max }\approx826.77\text{ }\frac{\text{ inch}}{\min} \end{gathered}$

Thus, the maximum speed is equivalent to 826.77 inches per minute.