(Matlab basic questions) Units and dB (show all work)
MAE$101B,$Spring$2020$Homework/Units$and$dB$ (show$all$work)$
$ 1) Convert$as$indicated$giving$answer$with$proper$sign$ figures.$ a. 7.550×103$km$to$feet$ b. 285$K$to$degrees$Fahrenheit$$ c. 6.85×104$ft$lbf$to$joules$ d. 14.7$lbf/in2$to$pascals$ e. 77.7$slug/ft3$to$grams$per$cubic$centimeter$ $
2) Using$the$rules$for$expressing$SI$units,$express$each$of$the$ following$in$correct$form$if$given$incorrectly$ a. 11.5$cms$ b. 475$N$ c. 9.5$m/s/s$ d. 5000$K$ e. 8,000$pa$ f. 25$amp$ g. 100.1$m$m$ h. 62.5$j$ i. 300$degrees$Kelvin$
$ 3) Compute$the$power$output$of$a$225$hp$engine$in$
a. British$thermal$units$per$minute$and$$ b. KiloVwatts$ $
4) Convert$a$mass$flow$rate$of$195$kg/s$(typical$airflow$ through$a$turbofan$engine)$to$slugs$per$minute$
$ 5) An$acoustic$wave$has$a$sound$pressure$level$(SPL)$of$80$ dB$re$1µbar$(Pref=1µbar).$Find$$ a. The$sound$pressure$level$re$1µPa$(Pref=1µPa)$ b. The$sound$pressure$level$re$20µPa$($Pref$to$20µPa)$
$ i. Hint:$SPL=20*log10(P/Pref)$ ii. 1µbar=0.1$N/m2=105µPa$
c. If$the$new$SPLnew$reading$is$18$dB$down$(62dB)$re$ 1µbar,$what$is$the$ratio$Pnew/P$equal$to$(P$pertains$ to$the$Pressure$at$80$dB)$
$ Extra&Credit:$A$graduate$student$working$for$SpaceX$is$ interested$in$purchasing$microphones$to$measure$sound$ pressure$levels$(SPL)$for$the$development$of$the$human$ capsule.$The$output$of$any$sensor(microphones,$ accelerometers)$is$an$electrical$signal.$These$electrical$ quantities$are$often$specified$in$terms$of$levels.$The$voltage$ level$is$defined$as$VL(re$Vref)=20log10(V/Vref).$In$order$to$ convert$between$electrical$and$acoustic$(pressure)$quantities$ the$sensor$manufacturer$furnishes$the$sensitivity$data.$The$ sensitivity,$Mo,$of$a$microphone$is$defined$as$Mo=(V/P)$ (V=voltage,$P=pressure).$$This$sensitivity$is$usually$given$in$dB,$ and$this$term$is$usually$referred$as$sensitivity$level$ML(re& Mref)=20log10(Mo/Mref).$Please$show$the$graduate$student$that$ in$order$to$obtain$SPL$from$the$sensors$voltage$reading,$the$ following$equation$can$be$applied$ $ SPL(re$Pref)$=$VL(re$Vref)VML(re&Mref)+20log10(Vref/(Pref$*$Mref))$ $
