Physics (10th Edition)

According to the principle of energy conservation, $$E_f=E_0$$ $$(KE_f-KE_0)=-(PE_f-PE_0)$$ This principle applies when the forces concerned are conservative, which means the work done by the force, leading to the change in energy, is independent of the path between the object's initial and final positions. In short, here we have 3 different angles of release, yet since the height of release is the same, the tank's initial and final PE are the same. Similarly, in the 3 cases, the tank's initial velocity and kinetic energy are the same, so the final velocity and kinetic energy of the tank in the 3 cases will be the same, too. d) is correct.