here acceleration initially is given as 2 m/s/s for total time of 10 s
so in above situation the final speed will be 20 m/s
now here if acceleration is double as well as the time is also double
so now we will have
[tex]a = 4 m/s^2[/tex]
[tex]t = 20 s[/tex]
so now the final speed is given as
[tex]v_f = 4 (20)[/tex]
[tex]v_f = 80 m/s[/tex]