Physics Chapter 2: Motion, Forces, and Gravitation

Flashcards covering motion descriptions, forces, Newton's laws, gravitation, and momentum based on the lecture notes.

Motion

Change in an object’s position relative to a reference point over time.

Reference Frame

A chosen point or object that stays still while observing movement.

Distance

The total path traveled by an object.

Displacement

A straight-line change from a starting point to an ending point which includes direction.

Speed

A measure of how fast something moves; usually calculated as distance divided by time.

Velocity

Speed in a specific direction; changes when either speed or direction changes.

Acceleration

Describes how velocity changes, including speeding up, slowing down, or changing direction.

Average Speed

The result of $\text{total distance} \text{ / } \text{total time}$.

Instantaneous Speed

The speed of an object measured at a specific moment.

Force

A push or a pull that can make things move, stop, speed up, slow down, or change direction and shape.

Vectors

Quantities that have both size (magnitude) and direction, such as forces.

Balanced Forces

Equal pushes or pulls that cancel each other out, resulting in constant velocity or an object staying still.

Unbalanced Forces

Forces that do not cancel out, causing acceleration such as speeding up, slowing down, or turning.

Net Force

The sum of all the forces added together acting on an object; if it equals $0$, there is no change in motion.

Gravity

A force that pulls objects toward each other; specifically, Earth pulls objects downward.

Friction

A force that slows motion when surfaces rub together; rough surfaces create more of it than smooth surfaces.

Normal Force

A support force provided by a surface.

Applied Force

A push or pull exerted by a person or another object.

Tension

A pulling force found in ropes or strings.

Horizontal Motion

Movement across the ground analyzed independently from vertical motion.

Inertia

An object’s resistance to changes in its motion; a property of matter related to mass.

Newton’s First Law of Motion

Also called the Law of Inertia; states that objects stay at rest or keep moving in a straight line at constant speed unless acted on by an unbalanced force.

Acceleration due to Gravity

The downward acceleration of objects, which is approximately $9.8\,m/s^2$ on Earth.

Air Resistance

A force that pushes upward against falling objects; it increases with more surface area.

Terminal Velocity

The constant speed reached when air resistance becomes strong enough to balance the pull of gravity.

Compound Motion

Motion that happens in more than one direction at the same time, such as sideways and up/down.

Projectiles

Objects thrown or launched through the air that follow a curved, parabolic trajectory.

Newton’s Second Law

The law connecting force, mass, and acceleration using the equation $F = m \cdot a$.

Newton’s Third Law

The law of action and reaction; every force has an equal and opposite reaction force.

Weight

The force of gravity on an object, calculated with the equation $W = m \cdot g$.

Mass

The amount of matter in an object; it stays the same even if gravity changes.

Momentum

A measure of how hard it is to stop a moving object, defined by the equation $p = m \cdot v$.

Conservation of Momentum

A principle stating that in a closed system, the total momentum before a collision equals the total momentum after the collision.

Closed System

A system where no outside forces like friction or air resistance interfere.

Elastic Collision

A collision where objects bounce off each other and both momentum and kinetic energy are conserved.

Inelastic Collision

A collision where objects stick together or deform; momentum is conserved but kinetic energy is not.

Impulse

The change in momentum caused by a force acting over a period of time, calculated as $J = F \cdot t$.

Centripetal Force

An inward force, such as gravity or friction, that keeps an object moving in a circle.

Centripetal Acceleration

The inward acceleration of an object in circular motion caused by constant change in direction.

Centrifugal Force

A fictitious or apparent outward force felt in a rotating frame, which is actually caused by the body’s inertia.

Newton’s Law of Gravitation

States that everything with mass attracts everything else according to the equation $F = G \frac{m_1 m_2}{r^2}$.

Inverse-square Law

The physical principle stating that gravitational force decreases rapidly as the square of the distance between objects increases.