Pounds Mass vs. Force
Ben, thanks for your comment on this matter from Australia. When I was first starting my engineering career in the early 1960's, I thought the US would make the transition before 1975. Boy, was I ever mistaken. I think now the US is farther from making the transition than it was in 1960, and that is really bad. Last I heard, there was the US and one or two really undeveloped 3rd world countries still using feet and inches (in the US we refer to it as US Customary Units, every one else will know this as Imperial Units). This is probably one of the factors causing the very adverse balance of trade that the US is suffering right now (one of many, not the main factor). I wish I knew some way to light a fire under the process in the US to get SI moving!