Deceleration Vs time and distance

[nogsta]

An object decelerates from 20 m s to 10 m s. Deceleration is a constant 2.50 m s−2.

Firstly, time taken. change in speed over deceleration? Would make it 4 seconds. Is that correct?

Secondly how do I calculate the distance covered? Is it simply change in speed x time
which would make it 40 m? Or is it more complicated than this?

 

[aim1732]

No. Distance is velocity times time elapsed(and not change in velocity). Since velocity changes you should integrate for distance.