Afraid of losing contact with the bike in the air?
Below is the transcription of the video text.
The first times I tried to jump on a mountain bike, following the instructor's directions, I was afraid of losing contact with the bike as soon as the wheels left the ground. Using pedals without attacks, the prevailing fear was to lose contact with them ending up in a painful landing. The good instructor urged me not to be afraid, telling me that the bike would follow me on the flight and he was right!
In the video "MTB Jumps – a matter of PHYSICS !!!" we realized that when we jump we follow a parabolic trajectory whose shape depends exclusively on the speed that you have at the moment you leave the ground. Neglecting the friction of the air, we have also seen that the mass of the bike-rider system plays no role: this is the key concept that you need to convince yourself not to be afraid of losing your bike in the air.
Since mass does not affect the shape of the trajectory, we can imagine that if the bike made the jump on its own, without a rider, it would still follow the same parable. You could therefore convince yourself that during the flight you are not dragging the bike, it is the bike that travels with you along the same trajectory. To get the practical demonstration of this thesis, we could try to leave the grip while in the air and check if the bike keeps moving with us or not.
Luckily someone's already tried and we have proof of that! In these videos we see the athletes leaving the grip in the air for a few moments, and then holding the bike again without any particular problem. The trick, therefore, shows that the bike follows the rider regardless of his grip. During the fall the same behavior is observed, the bike falls exactly together with the rider, although he pushes it away to avoid falling on it.
In the most acrobatic disciplines, when in mid-air the athlete realizes that he cannot close a jump, he pushes the bike away to avoid falling on it, precisely because of this. If it is not pushed away, since it makes the same trajectory as the rider, it will end up touching the ground at the same point as the rider, and he will inevitably fall on it, with greater injury risk.
If you are interested in the topic, more details can be found by reading "The science of Mountain Bike riding: the physics behind MTB skills" which contains all the topics, addressed to all MTB enthusiasts.
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