Question

If a car is traveling at 20m/s, and then decelerates at 4m/s/s, how long does it take to stop

Answer 1

Given,
u = 20m/s
v= 0
a = -4m/s/s
To find, 
           t = (v- u)/a    [a= (v-u)/t]
              = -20/-4
               = 5 seconds

Answer 2

I think the answer is this Sir