Question

a quantity us measured is-20m/'s. is it speed or velocity

Answer 1

it would be velocity as it is negative and has a direction

Answer 2

Hello Dear !
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The quantity measured -20m/s is velocity .
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As you know Speed   = scalar quantity 
                     Velocity = Vector quantity 
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velocity can be negative 
but speed cant be negative because 
velocity = displacement /time
speed   = distance        / time 
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Displacement can be negative so velocity can also be negative 
but distance is always positive so speed is always positive 
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