Definitions
Ch 9 (A)
Ch 9 (A)
Impulse
Force multiplied by the time during which the force acts. Athletes vary the amount of muscular force and the period over which this force is applied.
Concentric
A type of muscle activation where the muscle generates force while shortening. Examples of concentric contractions include lifting a weight during a bicep curl, pushing up in a push-up, or standing up from a squat.
Impulse
J (or Imp) = F ⋅ t
N⋅s
Momentum
Quantity of motion. The mass of an object multiplied by its velocity. An increase in the mass or the velocity of an athlete increases the athlete’s momentum.
Eccentric
A type of muscle contraction where the muscle lengthens while still generating force. This type of contraction is common in everyday activities like slowing down during a run, walking downhill, or controlling the descent of a weight during a weightlifting exercise.
Momentum
M = m ⋅ v
kg⋅m/s
Work
A measure of how much force has been applied over a certain distance.
Isometric
A type of muscle contraction where the muscle length remains constant while the muscle is generating force. Planks, wall sits, and holding a weight at a constant position are all examples of isometric exercises.
Work
W = F ⋅ x
Joule (J)
Power
A measure of how much work has been done over a certain period.
Energy
In mechanics, energy is the ability to do mechanical work. The more energy an object or athlete has, the greater the force with which it can shift or deform another object or athlete.
Power
P = W / t
Watt (W)
Friction
A measure of the resistance to movement. A force that acts in opposition to the movement of one surface on another.
Kinetic Energy
The ability of an object or athlete to perform work by virtue of being in motion. Doubling the mass of an object increases its kinetic energy twofold. Doubling the velocity of an object increases its kinetic energy fourfold.
Kinetic Energy
KE = ½m ⋅ v2
Joule (J)
Elastic Potential Energy
A form of potential energy stored in an object when the object is distorted or deformed. An archer’s bow and a pole-vaulter’s pole store strain energy.
Gravitational potential energy
The energy that an object possesses by virtue of being within the earth’s gravitational field and above the earth’s surface. The more mass an object has and the greater the height it is above the earth’s surface, the more gravitational potential energy the object possesses.
Friction
Fk = μ ⋅ Fn
Newtons (N)
Horsepower
A term introduced by inventor James Watt and used as a measurement of power in the imperial (English) system of measurement.
Conservation of Linear Momentum
In any collision between two objects or two athletes, the total amount of momentum before the collision is the same after the collision. Momentum is conserved.
Elastic Potential Energy
Ee = ½k ⋅ x2
Joule (J)
Coefficient of Restitution
A measure of the ability of an object like a ball to spring back to its original shape after being hit by a club, bat, or racket or after bouncing off a floor or a wall. It is essentially a measure of bounciness or resilience.
Dissipation of Kinetic Energy
In any collision between two objects or two athletes, the kinetic energy brought into the collision is dissipated in the following manner: Some kinetic energy is used by the objects and the athletes in performing work on each other during the collision. But kinetic energy is also lost as heat and noise. See also the law of the conservation of energy.
Gravitational Potential Energy
Eg = m ⋅ g ⋅ h
Joule (J)