The physics classroom tragedy we've all experienced! Tom (labeled "Me") is speeding toward certain doom because he forgot to convert to SI units, while Jerry (labeled "Correct Answer") sits safely on the other track. Newton is probably rolling in his grave watching students use miles per hour instead of meters per second in equations.
In scientific calculations, using non-SI units is basically asking for disaster. One moment you're solving a simple physics problem, the next you're accidentally crashing a $125 million Mars orbiter because someone used imperial units. Classic physics student self-sabotage!