Physics Practice Test 2: Dynamics, Circular Motion, and Gravitation

Vocabulary practice flashcards covering Newton's laws of motion, friction, uniform circular motion, gravitation, orbital mechanics, work, and apparent weight.

Newton's First Law (Equilibrium Condition)

The principle stating that an object moving at a constant velocity experiences a net external force of zero ($\Sigma \mathbf{F} = 0$).

Newton's Third Law of Motion

The law stating that for every action force, there is an equal in magnitude and opposite in direction reaction force between interacting bodies.

Centripetal Acceleration

The inward acceleration experienced by an object traveling with constant speed along a circular path, directed radially toward the center of curvature.

Centripetal Force on an Unbanked Curve

The static friction force directed perpendicular to the road curve inward toward the center of curvature that enables a car to negotiate a horizontal turn.

Centripetal Force on a Banked Curve

The horizontal component of the normal force exerted by the inclined road surface that provides the necessary inward force to navigate the turn without relying on friction.

Constant Net Force Motion

A state of motion wherein an object subject to an unchanging non-zero net force experiences constant (uniform) acceleration ($a = \frac{F_{net}}{m}$).

Mass vs. Weight

Mass is an invariant measure of inertia that remains constant regardless of location, whereas weight is the gravitational force ($W = m g$) acting on that mass and varies with local gravitational acceleration.

Work Done by Gravity on a Horizontal Surface

A quantity of zero work ($W = 0$) because the downward force of gravity acts perpendicular ($90^\circ$) to the direction of horizontal displacement, causing no change in the system's energy.

Kinetic Energy Velocity Dependence

The direct proportionality of kinetic energy to the square of speed ($KE = \frac{1}{2}m v^2$), which causes kinetic energy to increase by a factor of 9 when speed is tripled.

Newton's Law of Universal Gravitation

The law stating mutual gravitational attraction is proportional to the product of masses and inversely proportional to the square of their separation ($F = G \frac{m_1 m_2}{r^2}$); doubling both masses and doubling the distance leaves the attractive force unchanged ($F$).

Apparent Weightlessness

The physical sensation and condition experienced by astronauts in orbit caused by being in continuous free fall toward Earth along with their spacecraft, rather than an absence of gravity.

Motion Threshold on a Smooth Surface

The condition where friction is zero ($\mu = 0$), enabling any horizontal applied force greater than zero to set an object into motion.

Surface Gravity Scaling

The relation $g = \frac{G M}{R^2}$, dictating that a hypothetical planet with half of Earth's mass ($\frac{1}{2} M$) and twice Earth's radius ($2 R$) has a surface gravity equal to $\frac{g}{8}$.

Kepler's Second Law (Elliptical Orbital Speed)

The orbital mechanics rule dictating that an object in an eccentric orbit (such as Halley's Comet) increases in orbital speed as it nears the Sun and slows as it recedes.

Kepler's Third Law Ratio

The constant ratio $\frac{T^2}{R^3}$ relating the square of the orbital period ($T$) to the cube of the orbital radius ($R$) for all bodies orbiting a common central body in circular paths.

Normal Force with Downward Applied Force

The normal force exerted on a block when an external force is directed downward at an angle $\theta$ below the horizontal: $F_N = m g + F_{app} \sin(\theta)$.

Apparent Weight in an Elevator

The contact force recorded by a scale supporting a person ($F_N = m(g + a)$), which exceeds true weight during upward acceleration ($a > 0$) and equals true weight ($m g$) when traveling at constant speed ($a = 0$).