Translating "for", as in "with"
'for' in your sentence functions more like 'about' than 'with'.

F=ma


for 'm' the mass and (for) 'a' the acceleration = about 'm', it refers to mass; about 'a', it refers to 'the acceleration'


至于'm', 指的是质量, 至于'a', 指的是加速度 --&gt; 'm', 指的是质量, 'a' 指的是加速度 (omit 至于 in this sentence make it sound more natural in Chinese)

If you want to use 'with' instead, your sentence would become

F=ma


with 'm' (as) the mass and with 'a' (as) the acceleration


以'm'(为)质量, 以'a'(为)加速度

I think the sentence below is easier to translate

F=ma


'm' represents the mass and 'a' represents the acceleration


'm' 代表质量，'a' 代表加速度