Physics is an integral part of skateboarding .
Having an understanding of some of the basic physics forces can help you to understand how skateboarding tricks are performed ,
therefore giving you an increased understanding of skateboarding and your possibilities .
Newton's Laws of Motion can be used to explain how the transformation of energy through your body is used , through to building up speed ,
all the way through to manipulating the skateboard's center of gravity to help it stick to your feet during flight , and how the board flips and spins
and not forgetting the physics behind grinds and slides
conservation of linear momentum -
The law of conservation of linear momentum is a fundamental law of nature, and it states that the total momentum of a closed system of objects
(which has no interactions with external agents) is constant.
One of the consequences of this is that the center of mass of any system of objects will always continue with the same velocity unless acted on by a force from outside the system.
Conservation of momentum is a mathematical consequence of the homogeneity (shift symmetry) of space (position in space is the canonical conjugate quantity to momentum). So, momentum conservation can be philosophically stated as ( nothing depends on location per se ).
In an isolated system (one where external forces are absent) the total momentum will be constant
this is implied by Newton's first law of motion. Newton's third law of motion, the law of reciprocal actions, which dictates that the forces acting between systems are equal in magnitude, but opposite in sign, is due to the conservation of momentum.
Since position in space is a vector quantity, momentum (being the canonical conjugate of position) is a vector quantity as well - it has direction.
Thus, when a gun is fired, the final total momentum of the system (the gun and the bullet) is the vector sum of the momenta of these two objects. Assuming that the gun and bullet were at rest prior to firing (meaning the initial momentum of the system was zero), the final total momentum must also equal 0.
conservation of angular momentum -
Objects executing motion around a point possess a quantity called angular momentum.
This is an important physical quantity because all experimental evidence indicates that angular momentum is rigorously conserved in our Universe:
It can be transferred, but it cannot be created or destroyed.
For the simple case of a small mass executing uniform circular motion around a much larger mass (so that we can neglect the effect of the center of mass) the amount of angular momentum takes a simple form.
In physics, the angular momentum of an object rotating about some reference point is the measure of the extent to which the object will continue to rotate about that point unless acted upon by an external torque. In particular, if a point mass rotates about an axis, then the angular momentum with respect to a point on the axis is related to the mass of the object, the velocity and the distance of the mass to the axis.
Angular momentum is important in physics because it is a conserved quantity: a system's angular momentum stays constant unless an external torque acts on it. Torque is the rate at which angular momentum is transferred in or out of the system. When a rigid body rotates, its resistance to a change in its rotational motion is measured by its moment of inertia. Angular momentum is an important concept in both physics and engineering, with numerous applications. For example, the kinetic energy stored in a massive rotating object such as a flywheel is proportional to the square of the angular momentum. Conservation of angular momentum also explains many phenomena in sports and nature.
In a closed system angular momentum is constant. This conservation law mathematically follows from continuous directional symmetry of space (no direction in space is any different from any other direction).
The time derivative of angular momentum is called torque
If a planet is found to rotate slower than expected, then astronomers suspect that the planet is accompanied by a satellite, because the total angular momentum is shared between the planet and its satellite in order to be conserved.
The conservation of angular momentum is used extensively in analyzing what is called central force motion. If the net force on some body is directed always toward some fixed point, the center, then there is no torque on the body with respect to the center, and so the angular momentum of the body about the center is constant. Constant angular momentum is extremely useful when dealing with the orbits of planets and satellites, and also when analyzing the Bohr model of the atom.
The conservation of angular momentum explains the angular acceleration of an ice skater as she brings her arms and legs close to the vertical axis of rotation. By bringing part of mass of her body closer to the axis she decreases her body's moment of inertia. Because angular momentum is constant in the absence of external torques, the angular velocity (rotational speed) of the skater has to increase.
The same phenomenon results in extremely fast spin of compact stars (like white dwarfs, neutron stars and black holes) when they are formed out of much larger and slower rotating stars (indeed, decreasing the size of object 104 times results in increase of its angular velocity by the factor 108).
The conservation of angular momentum in Earth-Moon system results in the transfer of angular momentum from Earth to Moon (due to tidal torque the Moon exerts on the Earth). This in turn results in the slowing down of the rotation rate of Earth (at about 42 nsec/day), and in gradual increase of the radius of Moon's orbit (at ~4.5 cm/year rate).
A conservation law is a statement used in Physics that says that the amount of something does not change in time. That thing could be as simple as mass or charge, or something that has to be calculated, like energy, or angular momentum.
For example, the law of conservation of mass is the conservation law that says that the amount of mass is always conserved, even if it is changed into another form. This means that if the mass of the universe could be measured right now, its mass would be known tomorrow because it will not change.
For a long time, people thought that these laws were true for the amount of mass and energy in the universe. Later on, Albert Einstein said that they were not completely true. He said that mass could change into energy (or the other way around). If this happened, it would be against the conservation laws because if mass was changed into energy, the total amount of mass goes down, and the total amount of energy goes up.
Einstein said that conservation laws could still be used if all the mass and all the energy were combined. He said that even though the mass changes or the energy changes, the sum when they are added together does not change. So now there is just one conservation law for mass and energy together.
Of course, mass is measured in kilograms, and energy is measured in joules. They cannot be added together directly, but Einstein found a way to add them together. He created the equation E = mc2. This equation means is that before adding the amount of mass to the amount of energy, the mass must be multiplied by the speed of light and then by the speed of light again.
Some of the things that are thought to be conserved are:
Conservation laws are helpful for people when they do problems in Physics. This is because if they know that a thing is conserved, it gives them more mathematical information about the thing they are doing the problem about.
Because science does not know where consciousness originally comes from, some mystic philosophers have guessed that there may also be a law of conservation of consciousness in the universe. That is to say, when something loses consciousness, or dies, that consciousness may not disappear, but may go into some kind of unseen pool of consciousness, according to this idea.
Conservation laws can come in two types, global, or local.
Global conservation
A global conservation law just says that the total amount of something in the universe does not change in time.
Local conservation
A local conservation law says a little bit more than that. It says that if the amount of something changed in one place, it's because it moved in to or out of that place, and we can measure that movement.
Newton's 2nd Law and centripetal force and acceleration -
The following forces are used in skateboarding
centripetal force : a force that keeps a body moving in a circular path
rotational inertia : a measure of an object’s resistance to being turned, depending on both the mass of the object and how that mass is distributed
work : force applied over a distance—for example,
you do work when you push a box across the floor, but not when you push on a locked door;
work done on an object or system results in an increase in the energy of that system