Related Research Articles
In physics, a force is any influence that, when unopposed, will change the motion of an object. A force can cause an object with mass to change its velocity, i.e., to accelerate. Force can also be described intuitively as a push or a pull. A force has both magnitude and direction, making it a vector quantity. It is measured in the SI unit of newton (N). Force is represented by the symbol F.
Friction is the force resisting the relative motion of solid surfaces, fluid layers, and material elements sliding against each other. There are several types of friction:
The high jump is a track and field event in which competitors must jump unaided over a horizontal bar placed at measured heights without dislodging it. In its modern, most-practiced format, a bar is placed between two standards with a crash mat for landing. Since ancient times, competitors have introduced increasingly effective techniques to arrive at the current form, in which athletes run towards the bar and use the Fosbury Flop method, leaping head first with their back to the bar.
An inclined plane, also known as a ramp, is a flat supporting surface tilted at an angle, with one end higher than the other, used as an aid for raising or lowering a load. The inclined plane is one of the six classical simple machines defined by Renaissance scientists. Inclined planes are widely used to move heavy loads over vertical obstacles; examples vary from a ramp used to load goods into a truck, to a person walking up a pedestrian ramp, to an automobile or railroad train climbing a grade.
In classical mechanics, Newton's laws of motion are three laws that describe the relationship between the motion of an object and the forces acting on it. The first law states that an object either remains at rest or continues to move at a constant velocity, unless it is acted upon by an external force. The second law states that the rate of change of momentum of an object is directly proportional to the force applied, or, for an object with constant mass, that the net force on an object is equal to the mass of that object multiplied by the acceleration. The third law states that when one object exerts a force on a second object, that second object exerts a force that is equal in magnitude and opposite in direction on the first object.
Calisthenics or callisthenics is a form of strength training consisting of a variety of movements that exercise large muscle groups, such as standing, grasping, pushing, etc. These exercises are often performed rhythmically and with minimal equipment, as bodyweight exercises. They are intended to increase strength, fitness, and flexibility, through movements such as pulling, pushing, bending, jumping, or swinging, using one's body weight for resistance. Calisthenics can provide the benefits of muscular and aerobic conditioning, in addition to improving psychomotor skills such as balance, agility, and coordination.
Archimedes' principle states that the upward buoyant force that is exerted on a body immersed in a fluid, whether fully or partially, is equal to the weight of the fluid that the body displaces. Archimedes' principle is a law of physics fundamental to fluid mechanics. It was formulated by Archimedes of Syracuse.
A free body diagram consists of a diagrammatic representation of a single body or a subsystem of bodies isolated from its surroundings showing all the forces acting on it. In physics and engineering, a free body diagram is a graphical illustration used to visualize the applied forces, moments, and resulting reactions on a body in a given condition. They depict a body or connected bodies with all the applied forces and moments, and reactions, which act on the body(ies). The body may consist of multiple internal members, or be a compact body. A series of free bodies and other diagrams may be necessary to solve complex problems.
In mechanics, the normal force is the component of a contact force that is perpendicular to the surface that an object contacts, as in Figure 1. In this instance normal is used in the geometric sense and means perpendicular, as opposed to the common language use of normal meaning "ordinary" or "expected". A person standing still on a platform is acted upon by gravity, which would pull them down towards the Earth's core unless there were a countervailing force from the resistance of the platform's molecules, a force which is named the "normal force".
In physics, apparent weight is a property of objects that corresponds to how heavy an object is. The apparent weight of an object will differ from the weight of an object whenever the force of gravity acting on the object is not balanced by an equal but opposite normal force. By definition, the weight of an object is equal to the magnitude of the force of gravity acting on it. This means that even a "weightless" astronaut in low Earth orbit, with an apparent weight of zero, has almost the same weight as he would have while standing on the ground; this is due to the force of gravity in low Earth orbit and on the ground being almost the same.
As described by the third of Newton's laws of motion of classical mechanics, all forces occur in pairs such that if one object exerts a force on another object, then the second object exerts an equal and opposite reaction force on the first. The third law is also more generally stated as: "To every action there is always opposed an equal reaction: or the mutual actions of two bodies upon each other are always equal, and directed to contrary parts." The attribution of which of the two forces is the action and which is the reaction is arbitrary. Either of the two can be considered the action, while the other is its associated reaction.
Plyometrics, also known as jump training or plyos, are exercises in which muscles exert maximum force in short intervals of time, with the goal of increasing power (speed-strength). This training focuses on learning to move from a muscle extension to a contraction in a rapid or "explosive" manner, such as in specialized repeated jumping. Plyometrics are primarily used by athletes, especially martial artists, sprinters, arm wrestlers and high jumpers, to improve performance, and are used in the fitness field to a much lesser degree.
A contact force is any force that requires contact to occur. Contact forces are ubiquitous and are responsible for most visible interactions between macroscopic collections of matter. Pushing a car up a hill or kicking a ball across a room are some of the everyday examples where contact forces are at work. In the first case the force is continuously applied by the person on the car, while in the second case the force is delivered in a short impulse. Contact forces are often decomposed into orthogonal components, one perpendicular to the surface(s) in contact called the normal force, and one parallel to the surface(s) in contact, called the friction force.
In thermodynamics, work performed by a system is energy transferred by the system to its surroundings, by a mechanism through which the system can spontaneously exert macroscopic forces on its surroundings. In the surroundings, through suitable passive linkages, the work can lift a weight, for example. Energy can also transfer from the surroundings to the system; in a sign convention used in physics, such work has a negative magnitude.
A vertical jump or vertical leap is the act of jumping upwards into the air. It can be an exercise for building both endurance and strength, and is also a standard test for measuring athletic performance. It may also be referred to as a Sargent jump, named for Dudley Allen Sargent.
Tiptoe describes the human body posture and locomotion of removing the heel(s) of one or both feet from the ground. The term is mostly used colloquially when the weight is placed on the balls of the feet rather than literally on the tips of the toes; literal tip-toeing is difficult but possible, as in the pointe technique of ballet. In running, landing on the ball of the foot is known as forefoot strike.
In classical mechanics, a reactive centrifugal force forms part of an action–reaction pair with a centripetal force.
In the context of classical mechanics simulations and physics engines employed within video games, collision response deals with models and algorithms for simulating the changes in the motion of two solid bodies following collision and other forms of contact.
Terrestrial locomotion by means of a running gait can be accomplished on level surfaces. However, in most outdoor environments an individual will experience terrain undulations requiring uphill running. Similar conditions can be mimicked in a controlled environment on a treadmill also. Additionally, running on inclines is used by runners, both distance and sprinter, to improve cardiovascular conditioning and lower limb strength.
Power training typically involves exercises which apply the maximum amount of force as fast as possible; on the basis that strength + speed = power. Jumping with weights or throwing weights are two examples of power training exercises. Regular weight training exercises such as the clean and jerk and power clean may also be considered as being power training exercises due to the explosive speed required to complete the lifts. Power training may also involve contrasting exercises such as heavy lifts and plyometrics, known as complex training, in an attempt to combine the maximal lifting exertions with dynamic movements. This combination of a high strength exercise with a high speed exercise may lead to an increased ability to apply power. Power training frequently specifically utilises two physiological processes which increase in conjunction with one another during exercise. These are deep breathing, which results in increased intra-abdominal pressure; and post-activation potentation, which is the enhanced activation of the nervous system and increased muscle fibre recruitment. Power training programmes may be shaped to increase the trainee's ability to apply power in general, to meet sports specific criteria, or both.
References
- ↑ "ground reaction force". Oxford Dictionary of Sports Science & Medicine, by Answers.com. Retrieved 2011-02-26.
- ↑ "Ground Reaction Force". Health Sciences Center, University of Oklahoma. 2002-04-03. Archived from the original on 2015-11-13. Retrieved 2009-02-24.
- ↑ Hyper Physics, http://hyperphysics.phy-astr.gsu.edu/hbase/frict2.html
- ↑ Ball, NB, Stock, CG, Scurr, JC. Bilateral Contact Ground Reaction Forces and Contact Times During Plyometric Drop Jump. Journal of Strength and Conditioning Research; October 2010 – Volume 24 – Issue 10- pp 2762-2769
| National libraries | |
|---|---|
| Other | |
