Solve free fall time and speed.
In free fall the only acceleration is gravity, so the impact speed follows from the kinematic relation v squared equals u squared plus 2gh, and the fall time from how long that speed change takes at acceleration g. Mass cancels out of both — a heavy and a light object reach the ground together in vacuum — but mass does determine the kinetic energy delivered on impact, which is what actually causes damage.
Free fall kinematics
v = sqrt(u^2 + 2 g h); t = (v - u) / g; kinetic energy = 0.5 m v^2
Gravitational force is proportional to mass and so is inertia, so the two cancel in Newton's second law. Doubling mass doubles the force but also doubles the resistance to acceleration.
No. It is the vacuum solution. Real drops deviate once speed approaches terminal velocity — about 55 m/s for a human in a spread position — so the calculation is accurate for dense, compact objects over short falls and increasingly optimistic beyond a few seconds.
It makes the non-linearity concrete. An object falls under 5 m in the first second but nearly 15 m in the second, because distance grows with the square of time rather than linearly.