A child operating a radio-controlled model car on a dock accidentally steers it off the edge. The car's displacement 0.58 s after leaving the dock has a magnitude of 7.1 m. What is the car's speed at the instant it drives off the edge of the dock?

Answer 1

What do you mean by displacement? Horizontal distance from the edge, or the actual slant distance (the resultant of vertical and horizontal components) from the edge?

I will assume the latter, since you refer to the magnitude.

In 0.58 s, the car will fall
Y = (g/2)*t^2 = 1.648 meters
The horizontal distance it will have moved is then
X = sqrt[(7.1)^2 - (1.648)^2] = 6.91 m
The car's speed at the edge would be
X/t = 6.91/0.58 = 11.9 m/s