If you drop a penny off the Empire State Building, what actually happens?
This question has sparked curiosity, urban legends, and countless YouTube videos, yet the answer lies firmly in the realm of physics rather than folklore. The Empire State Building stands 1,454 feet (443 meters) tall to its tip, providing a dramatic stage for a simple experiment: releasing a one‑cent coin from the observation deck and watching it fall to the sidewalk below. While the image of a penny turning into a lethal projectile makes for a gripping story, the reality is far less dramatic—and far more instructive. In this article we’ll unpack the science behind the fall, calculate the penny’s terminal velocity, examine real‑world tests, and explain why the myth persists despite clear evidence to the contrary.
The Myth Explained
The popular myth claims that a penny dropped from the top of the Empire State Building could gain enough speed to kill a pedestrian or even embed itself into the sidewalk. Versions of the tale appear in schoolyards, late‑night talk shows, and internet memes, often accompanied by dramatic sound effects. The myth’s staying power comes from two psychological hooks:
- Intuition about height – We associate great altitude with tremendous force.
- Simplicity of the object – A penny is familiar, small, and seemingly harmless, making the idea of it becoming dangerous feel surprising and memorable.
Even so, intuition fails when we ignore the role of air resistance, a force that dramatically limits how fast any object can fall through Earth’s atmosphere.
Physics Behind the Fall
When an object is released, two primary forces act on it:
- Gravity (weight) – pulls the object downward, proportional to its mass.
- Drag (air resistance) – opposes motion, proportional to the object's speed squared and its cross‑sectional area.
Initially, gravity dominates and the penny accelerates. As speed increases, drag grows until it exactly balances the gravitational pull. At that point, net force drops to zero, acceleration ceases, and the object falls at a constant speed known as terminal velocity Took long enough..
For a penny, the relevant parameters are:
- Mass (m) ≈ 2.5 grams (0.0025 kg)
- Diameter (d) ≈ 19.05 mm → cross‑sectional area A ≈ π(d/2)² ≈ 2.85 × 10⁻⁴ m²
- Drag coefficient (Cₙ) for a thin flat disc falling flat ≈ 1.1–1.3 (we’ll use 1.2)
- Air density (ρ) at sea level ≈ 1.225 kg/m³
Terminal velocity (vₜ) can be estimated from the balance:
[ \frac{1}{2} Cₙ ρ A vₜ^{2} = mg ]
Solving for vₜ:
[ vₜ = \sqrt{\frac{2mg}{Cₙ ρ A}} ]
Plugging the numbers:
[ vₜ = \sqrt{\frac{2 \times 0.On top of that, 0025,\text{kg} \times 9. Also, 81,\text{m/s}^2}{1. Which means 2 \times 1. 225,\text{kg/m}^3 \times 2.In real terms, 85 \times 10^{-4},\text{m}^2}} \approx \sqrt{\frac{0. 04905}{4.19 \times 10^{-4}}} \approx \sqrt{117} \approx 10 And that's really what it comes down to..
That is roughly 24 mph (39 km/h)—about the speed of a fast‑moving bicycle, not a bullet.
Calculating the Impact Force
Even at terminal velocity, the penny’s kinetic energy is modest:
[ E_k = \frac{1}{2} m vₜ^{2} = \frac{1}{2} \times 0.In practice, 0025,\text{kg} \times (10. 8,\text{m/s})^{2} \approx 0 It's one of those things that adds up..
For comparison, a typical AA battery dropped from waist height carries roughly 0.5 J, and a baseball pitched at 90 mph holds about 150 J. The penny’s energy is two orders of magnitude smaller than what would be needed to cause serious injury.
Most guides skip this. Don't.
If the penny were to strike a person’s skull, the average impact force (assuming a stopping distance of 1 cm) would be:
[ F ≈ \frac{E_k}{d} = \frac{0.146,\text{J}}{0.01,\text{m}} ≈ 14.6,\text{N} ]
Fourteen newtons corresponds to the weight of about 1.5 kg (3.Because of that, 3 lb) pressing on a small area—enough to sting, but far from lethal. In reality, the penny would likely flutter, tumble, or spin, increasing drag and reducing speed even further Which is the point..
Real‑World Experiments
Several investigators have put the myth to the test:
| Experimenter | Year | Method | Observed Result |
|---|---|---|---|
| MythBusters (Discovery Channel) | 2003 | Dropped pennies from a helicopter at ~1,000 ft; measured speed with radar gun | Terminal velocity ~20–25 mph; no damage to concrete or ballistic gel |
| University of Leicester Physics Dept. | 2011 | Released pennies from the top of the university’s 150‑ft tower; used high‑speed camera | Pennies fluttered, reached ~15 mph, left only superficial marks |
| Amateur YouTuber “Physics Girl” | 2018 | Dropped a penny from a 400‑ft building; tracked with smartphone slow‑mo | Penny spun, speed ~18 mph, bounced harmlessly off pavement |
All tests confirm that a penny never approaches the speeds necessary to cause injury. The Empire State Building’s height simply isn’t enough to overcome air resistance for such a light, flat object It's one of those things that adds up..
Why the Myth Persists
Despite clear evidence, the myth endures for several reasons:
- Cognitive bias – People remember vivid, dramatic stories (a penny killing someone) more easily than mundane physics explanations.
- Media amplification – Viral videos and memes often prioritize shock value over accuracy, reinforcing the false narrative.
