Mythbuster – Can a penny kill you?

By: Akshaya, Science Expo Ontario

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Myth:

Have you ever stood under the CN tower or any tall building for that matter and worry that you might be killed by a penny that was accidentally dropped off the top? Thankfully, we’re here to tell you that that is almost impossible! If a penny hit you after going off the edge of a very tall building, it would feel like someone flicked you on the forehead and not even a hard flick!

The Science Behind it:

A physicist named Louis Bloomfield, from the University of Virginia modelled this situation a few years ago with wind tunnels and helium balloons. He concluded through this experiment that it wouldn’t hurt.

The majority of people believe that when a penny is exposed to gravity, it will accelerate for the entire fall, reaching immense speeds by the time it hits the ground. However, this could only happen if there was no air and the penny was tossed in a vacuum. Therefore, theoretically, yes it can kill you. However, realistically, it cannot due to a number of factors.

One of the factors is drag force which is the collision that occurs between the molecules in the air. Drag force opposes gravitational pull. As the penny falls faster, it experiences the equal amount of air resistance. Therefore, even at its maximum velocity, the drag force still opposes the velocity. Since the two forces are balanced in this situation, the penny does not accelerate. It travels at a constant speed. This is known as terminal velocity.

Another factor is the physical nature of the coin. Pennies experience more air resistance due to their physical nature. They are flat, not very aerodynamic, and light. Therefore, it does not require much drag to slow it down.

It has been assumed that the falling penny accelerates 335 kph from a building such as the Empire State, but in reality it would only reach speeds of 40 kph.

Although a penny being able to kill you from its plummet from a tall building is a myth, it does contain a grain of truth. A penny may not hurt, but if a nail, a pen, or anything with a sharp or pointed edge hits a concentrated area on your head, it could kill you. So don’t relax with the head protection just yet! This may be a post for another time! Stay tuned.

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