You use a slingshot to launch a potato horizontally from the edge of a cliff with speed v0. The acceleration due to gravity is g. Take the origin at the launch point. Suppose that +y-axis is directed upward and speed v0 is in the +x-direction. How long after you launch the potato has it moved as far horizontally from the launch point as it has moved vertically?

 t = 2 v₀ / g

Explanation:

For this projectile launch exercise we use the displacement equations

        x = vox t

       y = y₀ + t - ½ g t²

As it is launched horizontally the vertical velocity is zero and the point of origin of the coordinate system is here, so y₀ is zero.

       x = v₀ t

       y = ½ g t²

They ask us for the time for which

        x = y

        vo t = ½ g t²

         t = 2 v₀ / g

f=ma newton

f=100x2.5=250n