A “negative speed” would be in fact a velocity.
ʌ WORD_BOUNDARY n ɛ ɡ ə t ɪ v WORD_BOUNDARY s p iː d WORD_BOUNDARY w ʊ d WORD_BOUNDARY b iː WORD_BOUNDARY ɪ n WORD_BOUNDARY f æ k t WORD_BOUNDARY ʌ WORD_BOUNDARY v ə l ɑ s ɪ t i WORD_BOUNDARY