T5 bulbs with T8 Ballasts
No t5 bulbs are 54w or t5ho are, T8 have a lower wattage 32w for example. 
The lamp may start but the ballast life and the lamp will be greatly reduced if it strikes (starts). 
Ballast are designed to limit the current to the lamp. They strike or ignight the gas in the tube , once the lamp starts the resistance starts dropping, the ballast limits the current and creates the strike voltage both of these are different when comparing t5 &amp; t8 lamps, so although it may work for a short time the lamp will not provide the rated light output, and the higher strike voltage needed for the longer T8 lamps may actually dammage the shorter t5 lamp. This is why the lamps and ballast need to be matched.