It’s a little less pithy, but it makes better sense nonetheless. The first equation describes your free fall. Your final velocity (Vf) is equal to your initial velocity (Vi) plus the acceleration you are undergoing (a) times the amount of time you are falling (t). In a free fall, the acceleration acting on you would be the acceleration due to Earth’s gravity (32.2 ft/s/s or 9.81 m/s/s). Multiplying this acceleration times the duration of the fall gives you a velocity at impact (taking into account your initial velocity).