A small toy starts moving from the position of rest under a...

Initial velocity of the particle is zero.

Applying equation of motion, we get $10 = \dfrac{1}{2} \times a \times {t}^{2}$

Let distance covered in next $ts$ is $x$.

Then, $10 + x = \dfrac{1}{2} \times a \times {\left(2t\right)}^{2}$

$⇒ 10 + x = \dfrac{1}{2}a{t}^{2} \times 4$

$⇒ 10 + x = 10 \times 4$

$⇒ x = 30m$