Mechanics

# Heaviness

Isn’t it true that at the lowest point on a roller coaster we feel like we’re heavier?

We are not able to feel our own weight. In reality, what we feel is the normal force acting on our body. In other words, what gives the sensation of heaviness is not the weight itself, but our normal weight.

We have the possibility to feel this sensation when we play on a roller coaster. When the cart passes the lowest point of the roller coaster, with very high speed, we have the impression that we are being squeezed in the seat, in this way, our body feels heavier than normal. Well, has our weight increased? No, it has not increased, because weight is nothing more than the product of mass and acceleration of gravity, so we know that in this game, neither our mass nor the acceleration of gravity change.

Why then the feeling of being heavier? This is because when the cart descends and makes the turn to reach the lowest part of the track, because of inertia, we have a natural tendency to escape on a tangent. Thus, we compress the bench we are sitting on more intensely and end up suffering a more intense reaction from the support. Using the language of physics, the normal force increases in value. Proving what has been said, we seem to be heavier not because our mass or weight has changed, but because the normal force responsible for the sensation of heaviness has increased in intensity.

Another interesting example of normal force acting is when someone falls from a great height. During the fall, one has a feeling of extreme lightness. Are you able to say why? When falling from a great height, a person spends a considerable time without compressing any surface. Thus, during this time interval, she no longer has the normal force acting on her body. As normal is responsible for the feeling of heaviness, when “losing it” we think we have also lost our weight.