Explanation :
It is given that the ad says the ride is 50 meters tall and reaches a speed of 28m/sec at the bottom.
The efficiency is defined as the ratio of the output energy and the input energy.
In this case, the output energy is kinetic energy and the input is potential energy.
Output energy, \(E_k=\dfrac{1}{2}\times mv^2\)
Input energy, \(E_p=mgh\)
Efficiency becomes :
\(E=\dfrac{1\times v^2}{2gh}\)
\(E=\dfrac{1\times (28\ m/s)^2}{2\times 9.8\ m/s^2\times 50\ m}\)
\(E=0.8\)
or
\(E=80\%\)
The ride is 80% efficient.