year 1 physics test

Density

ρ = m / V (Density = mass / volume)

Upthrust

Upthrust = weight of fluid displaced

Viscous Drag (Stokes' Law)

F = 6πηrv

Validity of Stokes' Law

For small spherical objects moving slowly through a fluid in laminar (non-turbulent) flow; viscosity must be constant

Viscosity Dependency

Temperature — viscosity decreases with increasing temperature (for liquids)

viscosity

Use the falling-ball method to determine the viscosity of a liquid by measuring terminal velocity and using Stokes' Law

Hooke's Law

∆F = k∆x (Force = spring constant × extension)

Stress Formula

Stress = Force / Cross-sectional area

Strain Formula

Strain = Change in length / Original length

Young Modulus Formula

Young modulus = Stress / Strain

Force-Extension Graphs

How a material stretches under load — linear at first (obeys Hooke's Law), then curves when plastic deformation begins

Limit of Proportionality

The point up to which force is directly proportional to extension (obeys Hooke's Law)

Elastic Limit

The maximum extension where a material can still return to its original shape when the load is removed

Yield Point

The point where a small increase in stress causes a large increase in strain (plastic deformation begins)

Elastic Deformation

Temporary deformation — material returns to original shape after load is removed

Plastic Deformation

Permanent deformation — material does not return to original shape after load is removed

Stress-Strain Graphs

How a material behaves under tension/compression; used to find Young modulus and breaking stress

Breaking Stress

The maximum stress a material can withstand before it breaks

younngs moduls pratical

Determine the Young modulus of a material by stretching a wire and measuring force, extension, and cross-sectional area

Elastic Strain Energy Formula

E_el = ½ F∆x

Alternative Calculation for Elastic Strain Energy

From the area under the force-extension graph

Amplitude

The maximum displacement of particles from their equilibrium position.

Frequency (𝑓)

The number of oscillations per unit time (measured in Hz).

Period (𝑇)

The time taken for one complete oscillation (measured in seconds).

Speed (𝑣)

The rate at which the wave propagates through the medium (measured in m/s).

Wavelength (𝜆)

The distance between two consecutive points in phase (e.g., crest to crest or trough to trough).

Wave Equation

The wave equation is 𝑣=𝑓𝜆, where 𝑣 is the wave speed (m/s), 𝑓 is the frequency (Hz), and 𝜆 is the wavelength (m).

Longitudinal Waves

In longitudinal waves, particles of the medium move in the same direction as the wave, causing pressure variations. Molecules compress and rarefy along the direction of wave propagation.

Transverse Waves

In transverse waves, particles of the medium move perpendicular to the direction of wave propagation. The wave has crests and troughs (e.g., light, water waves).

Graphs of Waves

Transverse wave: The displacement is perpendicular to the direction of wave travel (e.g., sine wave). Longitudinal wave: The displacement is parallel to the direction of wave travel (e.g., compressions and rarefactions).

Standing Waves

Standing waves are formed when two waves of equal frequency and amplitude traveling in opposite directions interfere. They have nodes (no displacement) and antinodes (maximum displacement).

Speed of Sound Practical

Set up the speaker and microphone at a fixed distance. Use the oscilloscope to measure the time for a sound wave to travel from the speaker to the microphone. Calculate the speed of sound using 𝑣=𝑓𝜆, where 𝑓 is the frequency of the signal generated by the signal generator and 𝜆 is the wavelength from the measurement.

Diffraction

Diffraction is the bending of waves around obstacles or through slits.

Huygens' construction

Every point on a wavefront acts as a source of secondary waves (secondary wavelets) that spread out, causing the wave to bend when it encounters an obstacle or slit.

Diffraction Grating Equation

The equation used to analyze diffraction patterns from a diffraction grating is nλ=dsinθ, where n is the diffraction order, λ is the wavelength, d is the separation between adjacent slits, and θ is the diffraction angle.

Measuring Wavelength Using Diffraction Grating

To determine the wavelength of light using a diffraction grating, shine light through the diffraction grating and observe the resulting diffraction pattern. Measure the angle θ for the first-order diffraction and use the diffraction grating equation nλ=dsinθ to calculate the wavelength λ.

De Broglie Equation

The de Broglie equation is λ=ℎ/p, where λ is the de Broglie wavelength, ℎ is Planck's constant, and p is the momentum of the particle.

Diffraction and Wave Nature of Electrons

Diffraction provides evidence for the wave nature of electrons, as when electrons pass through a crystal or slit, they produce a diffraction pattern similar to light waves.

Photon Energy Equation

The equation relating photon energy to wave frequency is E=hf, where E is the photon energy, h is Planck's constant, and f is the frequency of the electromagnetic wave.

Photoelectric Effect

The photoelectric effect occurs when light of sufficient frequency strikes a metal surface, causing the ejection of electrons, providing evidence that light behaves as particles (photons) with discrete energy levels.

Work Function and Threshold Frequency

Work function (ϕ): The minimum energy needed to release an electron from the metal's surface. Threshold frequency: The minimum frequency of light required to release an electron (when E=ϕ).

Electronvolt (eV)

1 electronvolt (eV) is the energy gained by an electron when it is accelerated through a potential difference of 1 volt. 1 eV=1.602×10−19 J.

Standing Waves in Strings

The frequency of a vibrating string increases with tension and decreases with length. The frequency is inversely proportional to the square root of mass per unit length.

SUVAT equations for 1D motion

v = u + at | s = ut + ½at² | v² = u² + 2as | s = (u + v)t/2

Gradient of a displacement-time graph

Velocity

Gradient of a velocity-time graph

Acceleration

Area under a velocity-time graph

Displacement

Area under an acceleration-time graph

Change in velocity

Scalar quantity

A quantity with magnitude only (e.g., speed, energy, mass)

Vector quantity

A quantity with magnitude and direction (e.g., velocity, force, momentum)

Resolve a vector into components

Fx = Fcosθ, Fy = Fsinθ

Resultant of two vectors at right angles

Use Pythagoras: R = √(F₁² + F₂²)

Independence of vertical and horizontal motion

Horizontal motion is at constant speed; vertical motion is under constant acceleration due to gravity

Free-body diagram

A diagram showing all forces acting on a body with arrows indicating direction

Newton's 2nd law

F = ma — Resultant force equals mass times acceleration

Terminal velocity

The maximum velocity when resistive forces balance weight (net force = 0)

Formulas for weight and gravitational field strength

W = mg and g = F/m

Determine acceleration due to gravity in a lab

Measure time and distance of a falling object and use s = ½gt²

Newton's 3rd law

For every action, there is an equal and opposite reaction on a different body

Equation for momentum

p = mv

Principle of conservation of momentum

Total momentum before = total momentum after in a closed system

Equation for moment of a force

Moment = Force × perpendicular distance (Fx)

Centre of gravity

Point where entire weight of an object acts

Principle of moments

Total clockwise moments = total anticlockwise moments in equilibrium

Equation for work done

Work = Force × displacement × cosθ

Equation for kinetic energy

Ek = ½mv²

Equation for gravitational potential energy

Egrav = mgΔh

Principle of conservation of energy

Energy cannot be created or destroyed, only transferred

Power equations

P = E/t and P = W/t

Equation for efficiency (energy)

Efficiency = useful energy output / total energy input

Equation for efficiency (power)

Efficiency = useful power output / total power input

Electric Current

I = Q / Δt (where I is the current, Q is the charge, and Δt is the time interval)

Electrical Power

P = VI (where P is power, V is voltage, and I is current)

Resistance

R = V / I (where R is resistance, V is voltage, and I is current)

Combining Resistors in Series

R_total = R1 + R2 + … (The total resistance is the sum of individual resistances in series.)

Combining Resistors in Parallel

1/R_total = 1/R1 + 1/R2 + … (The reciprocal of the total resistance is the sum of the reciprocals of the individual resistances.)

Ohmic Conductor

An ohmic conductor follows Ohm's Law (V ∝ I with constant resistance).

Non-Ohmic Conductor

A non-ohmic conductor (like a diode or filament bulb) does not have a linear relationship between current and voltage.

Diode Current Behavior

No current flows until the voltage exceeds the threshold (typically 0.7V for silicon diodes).

NTC Thermistor Behavior

The resistance decreases as the temperature increases (Negative Temperature Coefficient).

LDR Behavior

The resistance decreases as light intensity increases.

Electromotive Force (e.m.f.)

e.m.f. is the energy supplied by the source per unit charge.

Terminal Potential Difference

The potential difference across the terminals of the battery (which is lower than e.m.f. due to internal resistance).

Potential Divider

A potential divider is a circuit that uses two resistors to divide the input voltage into smaller, controllable output voltages.

Resistivity

ρ = R * A / l (where ρ is resistivity, R is resistance, A is cross-sectional area, and l is length of the wire)

Electrical Power with Resistance

P = I^2 * R (This is derived from P = VI and V = IR)

Current-Voltage Graph of Filament Bulb

It's non-linear, with the curve rising as the voltage increases. The resistance increases as the filament heats up.

Charge Conservation in Circuit

The total charge entering a junction must equal the total charge leaving the junction. Current is conserved at junctions (Kirchhoff's Current Law).

Energy Conservation in Circuit

The total energy supplied (e.m.f.) equals the total energy dissipated in the resistive components of the circuit.

I-V Graph for Diode

The graph shows no current below a certain threshold voltage, and then a sharp increase in current once the threshold voltage is exceeded (for a silicon diode, the threshold is around 0.7V).

Base quantities

Fundamental quantities such as length, mass, and time.

Derived quantities

Combinations of base quantities, for example, speed = m/s.

SI units of base quantities

m (metre), kg (kilogram), s (second), A (ampere), K (kelvin), mol (mole), cd (candela).

Practical skills in experiments

Using measuring instruments correctly, identifying variables, drawing conclusions, and evaluating reliability.

Estimating physical quantities

Use known reference values (e.g., human height ≈ 1.7 m), make logical assumptions, and apply them to problem-solving.

Limitations of physical measurements

Instrument resolution, human error, environmental conditions, reaction time, parallax error.

Applying limitations to practical work

By evaluating uncertainty, reducing systematic/random errors, and considering repeatability and reproducibility.

Communicating scientific ideas

Use appropriate physics terminology, labelled diagrams, units, significant figures, and structured explanations.

Applications and implications of science

Science can be used to develop technology, influence policy, improve lives, but also has ethical and environmental impacts.

Validating new knowledge in science

Through peer review, replication of results, publishing in journals, and scrutiny by experts.