Have you ever seen a trampoline? Better yet, have you ever been on one? The fun experience of having your feet touch the surface, lifting you into the air, giving a “flying” feeling for those few seconds. It sure is amazing, but have you ever wondered just how a trampoline does that?
Some think that it is the fabric-material of the trampoline surface that gives us the bounce effect, launching us into thin air, but it is not! The true key to the bounce that we get from trampolines are the system of springs attached to the surface.
Though a trampoline appears as nothing more than simple fun, it is truly an array of the law of physics. The science behind trampoline springs, commonly known as the trampoline effect, is the combinations of kinetic and potential energy, utilized with Hooke’s laws of elasticity, as well as Newton’s laws of motion. Before we dive into how this all works together, let’s first briefly discuss kinetic and potential energy!
Kinetic energy can be defined as the creation when an object with an amount of mass is moving with a given velocity (speed). When someone jumps on a trampoline, their body has kinetic energy that eventually changes over time. In other words, as you jump up and down on the trampoline, the kinetic energy increases or decreases with that person’s velocity, or speed. As someone is jumping on a trampoline, their kinetic energy is greatest as the body leaves the trampoline surface on the way up, and just before the feet hit the surface on the way down.
Potential energy is a type of stored energy that an object or objects encompass based on their size, shape, position, or even material that the object is made from. The equation used to calculate potential energy is as follows: PE (Potential Energy) is equal to the mass of the object multiplied by the gravity constant, multiplied with the height.
In terms of jumping on a trampoline, the higher object jumping on a trampoline bounces, the more potential energy said object has. As an object or body leaves a trampoline and ascends upward into the air, kinetic energy decreases and that energy is then transformed into potential energy. The opposite holds true as an object or body descends. As an object, lets say a person, is falling downwards towards the trampoline surface, potential energy decreases and is then transformed into kinetic energy.
Let us apply this knowledge to springs on a trampoline…
A spring is made with a coil-design. When someone jumps on a trampoline, the weight of the person forces the spring to coil downwards. This kinetic energy of jumping is applied to the springs, as it forces the trampoline downwards. As a result of the springs having pressure applied, or kinetic energy exerted onto it, we then apply Hooke’s laws of elasticity and equilibrium.
Robert Hooke was a 17th-century physicist who studied the actions and reactions of elasticity, including springs, and its properties. An elastic object, such as a spring, is one in which when stretched, it exerts a restoring force that brings it back to its original form and length. In his law, commonly referred to as Hooke’s law of elasticity, he states, “the force needed to extend or compress a spring by some distance scales linearly with respect to that distance”.
In sum, what Hooke is conveying is very simple: depending on the force you exert, or put, onto the spring, you will receive the same distance or length of pushback, or force, returned.
Let us apply this law to the trampolines. As you bounce harder on a trampoline, you are applying more force onto the springs, causing it to coil downwards more and extend further. This same distance of extension and force is then returned, causing the pushback, ultimately sending the person into the air as the spring coils upwards with the same force and distance as it was going downwards. Simply put, the harder the bounce, the more height you will achieve due to Hooke’s law. The higher you go, the more potential energy you will thus have!
It is important to note that Hooke’s laws are no exception to the laws of physics. In physics, one of the key principles is that “no material can be compressed or stretched beyond a maximum size”. Springs are no exception to this rule. This is why when you are bouncing on a trampoline, it is possible that you will reach a maximum height from a bounce that cannot be matched, or improved, to reach a higher distance. In simpler terms, your bounce will become constant and reach a maximum level due to the components of physics in general.
The final function to understanding how springs of a trampoline work to cause the bounce, or trampoline effect, is to utilize Isaac Newton’s laws of motion.
Isaac Newton was a mathematician and physicist who primarily studied gravity and in turn, became a leader in the physics world. In 1687, he published “Philosophiae Principles of Natural Philosophy”, which, with the universal law of gravity, became known as the three laws of motion. Newton’s three laws of motion state (1) Every object in a state of uniform motion will remain in that state of motion unless an external force acts upon it; (2) Force equals mass multiplied with acceleration; and (3) For every action there is an equal and opposite reaction.
Although all three of Newton’s laws apply to trampolines, it is more specifically his third law that is critical to trampoline springs. Newton’s third law of “equal and opposite reaction” is also commonly known as equilibrium, and the sole reason behind the pushback of the spring. In other words, as someone jumps downwards onto the trampoline, the spring is extended a certain distance at a certain pressure. When someone ascends, or gets lifted into the air, the spring reaches equilibrium by taking that same amount of distance and pressure, only this time it is in the opposite direction.
In summary, the true key behind the fun-filled flying feeling we receive from soaring high on a trampoline are the springs. Springs, with their coil shape and the law of physics and elasticity, are the key to everlasting fly-high bounces in trampoline parks, including Flight’s!
To experience fun and physics all in one, be sure to visit one of Flight’s locations!
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