If a freely falling rock were equipped with a speedometer, by how much would itd speed readings increase with each second if it were on a planet wreg=20m/s2?

" 20 m/s² " means that if gravity is the ONLY force on the object
(the object is in 'free fall'), then its speed increases by  20 m/s
every second.

That's the answer to your question.  Now, let me ask you
another one:

How does a speedometer tied to a falling rock work ?
How can it measure the rock's speed ?

Maybe one way would be to have a little tiny propeller on
the front of the speedometer, and it could measure how fast
the propeller is spinning as the rock falls through the air ?
Great idea.  But we already said the rock is in free-fall,
so there's no air resistance, we can't have any air, and
there's nothing to spin the propeller.

How would you do it ?  How can you measure the rock's speed ?

Acetic acid  /əˈsiːtɪk/, systematically named  ethanoic acid  /ˌɛθəˈnoʊɪk/, is a colourless liquid  organic compound  with the  chemical formula  ch3cooh (also written as ch3co2h or c2h4o2). when undiluted, it is sometimes called  glacial acetic acid.  vinegar  is no less than 4% acetic acid by volume, making acetic acid the main component of vinegar apart from water. acetic acid has a distinctive sour taste and pungent smell. in addition to household vinegar, it is mainly produced as a precursor to  polyvinyl acetate  and  cellulose acetate. it is classified as a  weak acid  since it only partially  dissociates  in solution, but concentrated acetic acid is corrosive and can attack the skin.acetic acidnamespreferred iupac nameacetic acidsystematic iupac nameethanoic acidother namesvinegar (when dilute); hydrogen acetate; methanecarboxylic acid[1][2]identifierscas number64-19-7  3d model (jsmol)interactive image3dmetb00009 reference506007chebichebi: 15366  chemblchembl539  chemspider171  drugbankdb03166  echa infocard100.000.528ec number200-580-7e numbere260  (preservatives)gmelin reference1380iuphar/bps1058keggd00010  meshacetic+acidpubchem  cid176rtecs numberaf1225000uniiq40q9n063p  un number2789inchiinchi=1s/c2h4o2/c1-2(3)4/h1h3,(h,3,4)  key:   qtbsbxvteameqo-uhfffaoysa-n  smilescc(o)=o