Oblique helps 245 Brazilians escape death when jumping at the same time

A group of 245 people ventured from 30m high bridge at Hortolandia, 110km northwest of Sao Paulo city, Brazil, to set a new world record on October 22, according to the International Business Times. The Guinness World Records Organization has not yet confirmed this record, but it has surpassed the performance of last year a Brazilian dance group also with 149 participants.

Participants hung on a cable, wearing a helmet, then jumped down at the same time. They dangled back and forth in the air until they stopped completely. Alan Fereira, the organizer of the show, said the group used a total of 20km of wires and 1,000 safety belts like professional climbing equipment.

The rope jump from the bridge down is slightly different from the Bungee dance, which is the rope cannot pull the jumper back to its original position due to lack of elasticity. The dancer is suspended at the end of the rope and must climb up the bridge through the same rope.

According to Live Science, 245 people who jumped from the bridge did not rely on the elasticity of the rope to absorb the kinetic energy but rely on the oscillation like a clock pendulum. Therefore, they still survive the dangerous jump.

If a person jumps from the bridge down along the rope vertically, he or she will have an acceleration of 9.8m / s ² . When the thread reaches the end of the length, the jumper stops suddenly and the rope is stretched. This can be dangerous.

245 people broke the "jump rope" record on the bridge in Hortolandia, Brazil, on October 22.(Photo: Reuters).

For example, a person falling from a height of 46m will move at a speed of about 113km / h at the end of the rope, and stop only for 1/10 second. This means they experience 32 times the acceleration of gravity, similar to crashing into a car. Newton's second law of motion states that the force acting on an object is equal to the mass of an object multiplied by acceleration. If the jumper has a 70kg mass stopped for 0.1 second, they will feel the force acting on the body equal to 21,910 Newton (N), equal to the weight of a small Asian elephant.

To overcome this problem, the group of adventurers tied one end of the rope below the bridge, to one side of the edge of the bridge, then tied the other end to the rope. They stood at the edge of the other bridge and jumped down.

At that time, the initial force of the rope on the jumper is not vertical but an oblique angle. The original kinetic energy of the dancer moves gradually into a potential position so it is not dangerous. The jumper vibrates like a clock pendulum before stopping due to friction with the air.