It looks like Soulver intentionally prevents seconds squared () from being represented at all. This makes doing physics difficult, as seconds squared often arise. For instance, acceleration (and hence force) have a seconds-squared in the denominator. For another example, computing the (unitless) gamma factor in relativity, will end up dividing two quantities with units , which Soulver refuses to evaluate. To get this to evaluate you must instead express as , which is annoying.

Ideally Soulver would just let all units be valid and leave it to the user to interpret them correctly, as any combination of units can arise in physics.