The dependence of the coordinate on time for a certain point is described by the equation x = 5 + 16 – 2t2.

The dependence of the coordinate on time for a certain point is described by the equation x = 5 + 16 – 2t2. At what moment in time is the projection of the point’s velocities on the OX axis equal to zero?

To understand the speed, you need to make the equation of speed from the equation of motion, and this is one derivative: U = -4t + 16 (Most likely you missed t about 16! Check the condition). We equate this expression to 0 and find the required time: 4t = 16 t = 4c
Answer: 2