Linear Kinetics, Work, Power, and Energy

Vocabulary flashcards covering linear kinetics, Newton's laws of motion, impulse, momentum, collisions, work, power, kinetic and potential energy, and mechanical energy conservation based on Chapters 3 and 4.

Kinetics

The branch of dynamics concerned with the forces that cause motion.

Newton's First Law of Motion (Law of Inertia)

The physical law stating that every body continues in its state of rest, or of uniform motion in a straight line, unless it is compelled to change that state by external forces impressed upon it.

Projectile

An object that has no external forces acting on it other than gravity.

Horizontal Motion of a Projectile

Motion characterized by a constant horizontal velocity and a straight-line horizontal path because gravity only affects the vertical component (assuming air resistance is negligible).

Newton's Second Law of Motion (Law of Acceleration)

The physical law stating that if a net external force is exerted on an object, the object will accelerate in the direction of the net external force, with acceleration proportional to the net external force and inversely proportional to its mass ($\Sigma F = m\,a$).

Vertical Motion of a Projectile

Motion governed by gravity causing a constant downward vertical acceleration of $9.81\,m/s^2$.

Newton's Third Law of Motion (Action-Reaction)

The physical law stating that for every action force exerted, there is an equal and opposite reaction force.

Impulse

The product of an average net force and the duration of time over which it acts ($\Sigma F \Delta t$), which produces a change in momentum.

Momentum ($M$)

The quantity of motion possessed by a body, measured as the product of its mass and velocity ($M = m\,v$).

Linear Momentum Equation

The formula equating impulse to the change in linear momentum: $\Sigma F \Delta t = m(V_f - V_i)$.

Impact

A collision of two bodies characterized by the exchange of a large force during a small time interval.

Perfectly Elastic Collision

An impact in which the relative velocities of two colliding bodies after impact are equal to their relative velocities before impact.

Perfectly Inelastic Collision

An impact in which at least one body deforms and does not regain its original shape, causing the bodies to remain together without separating.

Coefficient of Restitution ($e$)

A dimensionless number ranging from $0$ to $1$ that describes the relative elasticity of an impact, governed by $e = \frac{V_1 - V_2}{U_1 - U_2}$.

Coefficient of Restitution (Stationary Surface)

The relative elasticity index between a moving object and a stationary surface, calculated as $e = \sqrt{\frac{h_b}{h_d}}$, where $h_b$ is bounce height and $h_d$ is drop height.

Work ($W$)

Force applied against a resistance multiplied by the displacement of the resistance in the direction of that force ($W = F\,D$), expressed in Joules ($J$) or Newton-meters ($N \cdot m$).

Positive Work

Work done when an object is displaced in the same direction as the force acting on it, corresponding anatomically to concentric muscle contractions.

Negative Work

Work done when an object is displaced in the direction opposite to the force acting on it, corresponding anatomically to eccentric muscle contractions.

Isometric Contraction (Work Context)

A muscle contraction where muscle length remains unchanged, resulting in zero displacement and zero mechanical work.

Power ($P$)

The rate of work production, calculated as work divided by change in time ($P = \frac{W}{\Delta t}$) or force times velocity ($P = F\,v$), expressed in Watts ($W$).

Maximal Muscular Power Output

The peak power output produced by a muscle, occurring at a contraction velocity approximately equal to one-half ($\frac{1}{2}$) of the muscle's maximum contraction velocity.

Kinetic Energy ($KE$)

The energy an object possesses due to its motion, calculated as $KE = \frac{1}{2}\,m\,v^2$ and expressed in Joules ($J$).

Gravitational Potential Energy ($PE$)

The stored energy an object possesses due to its position relative to Earth, calculated as $PE = m\,g\,h$, where $g = 9.81\,m/s^2$.

Strain Potential Energy ($SE$)

The stored energy an object possesses due to deformation, calculated as $SE = \frac{1}{2}\,k\,x^2$, where $k$ is material stiffness and $x$ is deformation distance.

Law of Conservation of Mechanical Energy

The principle stating that when gravity is the only acting external force, a body's total mechanical energy ($PE + KE$) remains constant.

Work-Energy Relationship

The principle stating that work done by external forces (other than gravity) causes a change in total energy: $W = \Delta KE + \Delta PE + \Delta TE$.