Respuesta :

Answer:

t = 2 s

Explanation:

As we know that when object comes back to its initial position then the displacement of the object will be zero

so here we can say by kinematics equation

[tex]\Delta y = v_y t + \frac{1}{2}at^2[/tex]

here we know that

[tex]\Delta y = 0[/tex]

[tex]v_y = 9.8 m/s[/tex]

[tex]g = -9.8 m/s^2[/tex]

now from above equation we know

[tex]0 = 9.8 t - \frac{1]{2}9.8 t^2[/tex]

so from above equation we have

t = 2 s