Save the Egg is a competition to test the aerodynamics in parachutes and to assess which materials will work best as a parachute. Each student interested in taking part will have to assemble a parachute which will carry a egg. The competitor will build the parachute with the materials available. The objective is to release the parachute from the
4th floor to the patio without breaking the egg. The winners will get a prize!

Rules
1. The competitors can only use the materials provided to build the parachute.
2. All parachutes will be released from the 4th floor to the patio.
3. The competitor which manages to maintain the egg intact will be declared winner.
4. In case of a tie, the winner will be decided based on the time taken for the parachute to reach the ground (the longer, the better!)

Date - 11th of November period 5a

How to build your parachute?

Competitors, you will have various options of materials and your goal is to build the best parachute!
1. Choose the string (nylon, 'barbante')
2. Select the type of material (thick plastic, 'celofane', thin plastic and cloth)
3. Choose the type of cup (plastic, foam)
4. Build the parachute using the materials you chose, and you are ready to go!

Who are we?

Alvaro Mollica
Giuliana Silva
Ana Beatriz Oliva
Juliana Pereira
Miguel Arraes
Joao Pedro Maciel

Chemistry behind Parachutes

The choice of materials to make a parachute is essential for it to function well. Its main components are a fin fabric, suspension lines and support tapes. One essential feature is that the components have to have a low density. Density is defined as the mass of a material per unit volume and is normally measured in kg/m³ or g/cm³. So if there are two materials with the same volume , the one with the lowest mass, weight, and therefore the least dense one will be more beneficial for the parachute production because the denser the parachute, the faster will be the speed in which the chute will come down. So as density also depends on the mass of the materials, it’s better to use equipments with low relative molecular mass like carbon, nitrogen and hydrogen rather than elements with high molecular mass such as iron. That’s why most of the fibers used in parachutes are organic ones such as nylon 6,6 ([(-OC-( CH2)4-CO-NH-(CH2)6-NH-]n) , Terylene ([OC-(C6H6 )-CO – (CH2 )2 –O]n) and Kevlar( [C14H10N2O2]n). All of these fibers have a low density, hence, a low molecular mass and are strong, which are essential features for parachutes materials. The strength of, Kevlar, for example, is due not only because of the strength of the bonds but how the molecules are aligned. Kevlar is a polyamide and is made in a process called condensation polymerization. It’s produced, together with a water molecule, when reacting a molecule with two amines groups, which have the functional group NH2 , and a dicarboxylic acid. This polymer will contain a dipole-dipole bonding (C=O)and a hydrogen bonding (N-H) which are very strong bonds making the molecule strong. In addition to that, the molecules of the fiber are extended and perfect aligned. They need to be in a lattice chain configuration. This alignment also contributes to the stiffness and rigidity of the fiber making it more rigid. If you increase the rigidity of the material it will affect its shape which can then affect the stability of the parachute. If the parachute is stable then an air drag will be created and the parachute will descend slowly but if the parachute is unstable then the air drag won’t be produced and it will come down in a higher speed. The fact that the fiber made in parachutes is foldable, which means that it can be put in different shapes without breaking, is due to its malleability. This basically means that the layers of molecules are able to slide past each other rearranging the overall structure of the solid. Nylon and Terylene are also produced in condensation polymerization but nylon is a polyamide, like Kavlar, and Terylene a polyester ( polymer formed, together with a water molecule, by reacting diols (compounds containing two alcohol functional groups O-H) and dicarboxylic acids (compounds containing two carboxylic acids functional groups COOH).
Nylon is the material which is used the most to make parachute’s canopy because not only it has these characteristics of high strength, low density and high flexibility and rigidity but it’s also less expensive and more available than the other materials. Not only the canopy (top part of the parachute) but also the harness and the suspension lines (look at the pictures above) are made of nylon. The ripcord , the part you pull to open the parachute, is made of stainless steel and the metal connectors, used to join the suspension lines, are coated with cadmium, a d block element. Both the stainless steel from the ripcord and the cadmium coat from the connectors prevent rusting, which occurs when the iron or an alloy of iron reacts with oxygen in the presence of water. The cadmium serves as a coat and a sacrificial protection occurs, which is when a layer of a metal that is more reactive than iron, in this case, cadmium, is put over the iron metal so that as long as the “sacrificial” metal is present, it will corrode first. The stainless steel also contains a layer of chromium (III) oxide, which is more reactive than iron. This is another example of sacrificial protection.
When you practice these types of extremes sports, the hormone adrenaline starts to work in your body resulting in an adrenaline rush, which causes stress to the body. This hormone makes the blood vessels and air passages dilate. This will increase the concentration of blood into the muscle and of oxygen into the lungs. So as there’s a larger number of reactant particles in our body, therefore more collisions will happen more frequently. As there are more particles, the number of successful collisions will increase. These only occur when the particles have the activation energy, minimum energy needed for a reaction to take place. So if there are more successful collisions, more reactions inside our body will happen in a given time, increasing the rate of the reactions that happen in our body.

Physics behind parachutes

Physics:
For the egg not to break when it impacts the floor, its terminal velocity needs to be low enough, so that the egg’s skin can withstand the impact. That is, the parachute must decrease the egg’s terminal velocity enough for the impact with the floor to be weaker than what the egg’s skin can resist.
Terminal velocity is achieved, when the downward force of gravity is equal to the drag caused by the fluid in which the object is falling. In this case, the drag is doing a force upwards on the object. When the drag is equal to the force of gravity, there is no net force acting on the body and therefore there is no acceleration, leading to a constant velocity. This can be easily seen from the equation which connects force to acceleration:
it is obvious from this equation that when , .
Therefore, for this investigation, it is necessary to calculate the terminal velocity of the egg without a parachute and then, with the time taken of the different parachutes, compare and see which one did the best.

The density of air varies with temperature and therefore will be decided at the time of the experiment. The drag coefficient will also vary according to the shapes of the parachutes.
Using this equation it is possible to calculate the terminal velocity of the egg in the cup. Then with the terminal velocity, which will be the velocity it will hit the floor it will be possible to calculate the pressure which acts on the egg as it hits the floor. That is because the impact can be taken to an instant deceleration and that can be substituted into .
The area of the egg which hits the floor is then measured by drawing the parts of egg which touch a flat piece of paper. With this, the pressure acting on the egg can be calculated using .
The velocities of the falling eggs on different parachutes will be measured by timing the drop and measuring the height from which they are falling.

Following the equation above, the parachute which will result in the lowest terminal velocity will be that with the lowest density, that is, light weight and with a large surface area as its depth is almost negligible when calculating the density. The shape of the parachute will also affect its efficiency in slowing down the descent, as its drag coefficient will vary with its shape.

Biology behind parachuting

Adrenaline / Epinephrine
When parachuting, the skydiver may have the feeling of being extremely alert, energetic and responsive. This happens when humans and animals are faced with stressful, life-threatening situations. The reason is the secretion of adrenaline or epinephrine by the body as a response to stress and danger. The 'flight or fight' response of the body to threatening situations is aided internally by this hormone. It activates all the basic instincts of survival in humans.

Epinephrine enhances production of energy in the body, activates all the sensory processes to full alert as a priority and shuts down less important processes in that moment, like digestion. It leads to increase in blood sugar levels, higher heart rate and increase in blood pressure. It also starts energy production driving the body to the best possible levels of energy and concentration in order to achieve survival.

Effects of Epinephrine

Epinephrine is like the key or trigger for the activation of the survival instinct in the body. Once epinephrine is secreted by the body in the endocrine glands, it flows in the blood stream reaching various organ centers. It starts by activating some strategically placed receptors in the body. One by one, it activates these receptors which trigger the initiating of many chain reaction processes.

When epinephrine reaches the liver cells, it activates a receptor there which initializes a chain reaction that culminates into breaking down of glycogen, releasing glucose, an energy source in our body, into the blood stream. Simultaneously, it also activates the other liver receptors which again accelerates glucose production.

Receptors are also present in the muscles. When they are activated by epinephrine, they cause the widening of blood vessels so that more blood can reach the muscles for efficient operation, increasing the heart pumping rate.

On the other hand, when other receptors in muscles, when switched on by epinephrine, cause the narrowing or constriction of smooth muscles, resulting in decreased blood supply in some parts and increases resistance to blood flow in the arteries. This makes the skin pale, as less and less blood reaches it. This measure achieves conservation of body warmth.