Answer:
[tex]v=1.54\,\,metres\,\,per\,\,second[/tex]
Explanation:
The given equation is [tex]x=x_0+vt[/tex] where [tex]x_0[/tex] denotes initial time in the stopwatch and [tex]x[/tex] denotes the distance covered by car.
As the judge starts her watch at the instant the car passes the 2.0 meter mark [tex](x_0=2)[/tex] and the judge reads 3.9 seconds on her stopwatch when the car passes the 8.0 meter mark.
Put [tex]x_0=2,\,,\,x=8\,,\,t=3.9[/tex] in equation [tex]x=x_0+vt[/tex]
[tex]8=2+3.9t\\8-2=3.9t\\6=3.9v\\v=\frac{6}{3.9}\\ v=1.54\,\,metres\,\,per\,\,second[/tex]