Lecture Notes: Physics - Motion, Buoyancy, Electricity, Light, and Sound

Vocabulary flashcards covering key terms from Newtonian mechanics, buoyancy, Pascal’s principle, electricity safety, and the basics of light and sound.

Inertia

Property of matter that resists changes in its state of motion; an object at rest stays at rest and an object in motion stays in motion unless acted on by a net external force.

Net external force

The total force acting on an object from outside; required to change the object's motion.

Newton's First Law (Law of Inertia)

Objects resist changes in motion and maintain their state unless a net external force acts.

Newton's Second Law

The force acting on an object equals its mass times its acceleration (F = ma).

F = ma

The equation of Newton's Second Law: Force = mass × acceleration.

Mass

A measure of the amount of matter in an object; relates to inertia.

Acceleration

The rate of change of velocity over time.

Velocity

The rate of change of displacement; includes direction (v = displacement/time).

Displacement

The straight-line change in position from start to end; a vector.

Translational Motion

Straight-line motion of the whole object without rotation.

Rotational Motion

Spinning motion around an axis; different points have different speeds but share the same angular speed.

Angular displacement

The amount of rotation, θ.

Angular velocity

Rate of change of angular displacement, ω.

Angular acceleration

Rate of change of angular velocity, α.

Torque

Rotational equivalent of force; τ = Iα.

Moment of Inertia

I; resistance of a body to angular acceleration about an axis.

Rolling without slipping

A rolling object has both translational and rotational motion; v = rω.

v = r ω

Translational speed equals radius times angular speed for rolling without slipping.

Action–Reaction Law

For every action, there is an equal and opposite reaction.

Action–Reaction Pairs

Forces always come in pairs; one force acts on one object, the other on the interacting object.

Buoyant Force (Fb)

Upward force by a fluid on a submerged or floating object (Fb = ρ g V).

Archimedes’ Principle

An object immersed in a fluid experiences buoyant force equal to the weight of the displaced fluid.

Displacement (in buoyancy context)

When submerged, the fluid displaced by the object determines buoyant force.

Neutral buoyancy

Fb equals the object's weight; the object remains suspended in the fluid.

Density (ρ)

Density of the fluid, used in Fb = ρ g V.

Pascal’s Principle

Pressure applied to a confined fluid is transmitted equally in all directions.

Confined fluid

A fluid in a closed container where pressure changes are transmitted throughout.

Pressure (P)

P = F/A; pressure is force per unit area.

Force multiplication (hydraulics)

Same pressure across different areas allows a small force over a small area to create a larger force on a larger area.

Hydraulic jack

A device using Pascal’s principle to lift heavy loads.

Hydraulic brakes

Brake system where pedal force is transmitted to brake pads by fluid pressure.

Hydraulic lifts

Devices that use fluid pressure to lift heavy loads.

Dentist’s chair (hydraulic)

An example of hydraulic adjustment using fluid pressure.

Hydraulic presses

Machines that shape or compress materials using hydraulic pressure.

Overloading

Plugging too many devices into one outlet/circuit, drawing more current than wiring can safely handle.

Damaged insulation

Protective coating around wires wears away, exposing conductors; risk of shocks and short circuits.

Damp electrical conditions

Water near electrical equipment increases risk of shocks and short circuits.

Faulty wiring

Poorly installed or damaged wiring increasing risk of overheating and fires.

Electrocution

Death or severe injury caused by electric shock.

GFCI (Ground Fault Circuit Interrupter)

Safety device that shuts off power to prevent shock in wet/outdoor areas.

LED (Light Emitting Diode)

Semiconductor device that emits light; energy-efficient and long-lasting.

Phantom Load (Vampire Power)

Electricity consumed by devices even when turned off but plugged in.

kWh (kilowatt-hour)

Unit of energy; 1 kWh = energy used by 1000 W for 1 hour.

Energy efficiency

Using less energy to achieve the same result; LEDs are more efficient than incandescent bulbs.

Reflection

Light bounces off a surface; angle of incidence equals angle of reflection in regular reflection.

Angle of incidence

Angle at which incoming light strikes a surface.

Angle of reflection

Angle at which light reflects away from a surface (equal to the angle of incidence in regular reflection).

Regular reflection

Mirror-like reflection from smooth surfaces.

Diffuse reflection

Scattered reflection from rough surfaces.

Refraction

Bending of light as it passes between media with different speeds.

Medium

Material through which light travels (air, water, glass).

Diffraction

Bending or spreading of light waves around edges or through small openings.

Transmission

Light passing through a material.

Transparent

Allows most light to pass through with little scattering.

Translucent

Lets some light pass but scatters the rest.

Opaque

Blocks all light.

Absorption

Light energy taken in by a material and converted to heat or other forms.

Scattering

Redirection of light in different directions due to particles or irregularities.

Dispersion

Separation of white light into its component colors.

Rainbow

Visible spectrum produced by dispersion of light in droplets.

Spectrometer

Instrument used to analyze light by dispersion into component colors.

Pitch

Perceived highness or lowness of a sound; depends on the frequency of vibration.

Frequency (f)

Number of vibrational cycles per second; measured in Hz.

Loudness

Perceived strength of sound; depends on amplitude/energy of the wave.

Amplitude/Intensity

Height of a wave; related to loudness.

Quality (Timbre)

Character of a sound that distinguishes different sources with the same pitch and loudness; depends on waveform and harmonics.

Waveform

Shape of the sound wave; influences timbre.

Speed of sound (v)

Velocity of sound in a medium; depends on medium, density, and elasticity.

Echo

A reflected sound heard after a delay of about 0.1 seconds or more.

Reverberation

Multiple echoes overlapping; common in large spaces.

Resonance

When a system vibrates at its natural frequency due to an external sound wave.

Natural frequency

The frequency at which a system tends to vibrate in the absence of damping.

Tuning fork

A device that can demonstrate resonance when another object has a matching frequency.