Einstein's equation e = mc² indicates that the speed of light squared must be expressible in units of energy per unit mass. what is the value of the square of the speed of light in btu/lbm? in j/kg? the speed of light c 186,000 mi/s - 2.998 109 m/s. 1.21. a common basis for comparing rocket fuel systems is the specific impulse, defined as lbf of thrust produced divided by ibm/s of fuel and oxidizer consumed (see chap. 7). the common values are 250 to 400 lbf s/lbm. we frequently see the specific impulse referred to simply as "300 s." is 300 s the same thing as 300 lbf s/ lbm? european engi- neers regularly express the same quantity in terms of the equivalent exhaust velocity of the rocket. if a rocket has a specific impulse of 300 lbf s/ibm, what is its equivalen exhaust velocity? 1.22. most u. s. engineers work with heat fluxes with the unit btu/h in the rocket busi- ness the common unit is cal/(s cm"). how many btu/h ft) is i cal/(s the proper si unit is j/( m s). how many btu/h ft') = 1 /( ms)? 1.23. the reynolds number, discussed in chap. 6. is defined for a pipe as (velocity diameter density) / viscosity. what is the reynolds number for water flowing at 10 ft/s in a pipe with a diameter of 6 in? what are its dimensions?