Science 10 - Physics Notes

Units and Variables

  • Distance (d): metres (m), kilometres (km), etc.

  • Time (t): seconds (s), hours (h), etc.

  • Velocity/Speed (v): m/s, km/h

  • \Delta represents change. For example, \Delta v = v2 - v1

  • Acceleration (a): m/sĀ², km/hĀ²

  • Force (F): Newtons (N) = kgā€¢m/sĀ²

  • Work (W): Joules (J) = kgā€¢mĀ²/sĀ²

  • Potential Energy (Eā‚š): Joules (J)

  • Kinetic Energy (Eā‚–): Joules (J)

  • Mechanical Energy (Eā‚˜): Joules (J)

Rearranging Formulas

  • Example:- v = \frac{\Delta d}{\Delta t}

    • \Delta d = v \cdot \Delta t

    • \Delta t = \frac{\Delta d}{v}

  • Example:- F = ma

    • m = \frac{F}{a}

    • a = \frac{F}{m}

Unit Prefixes

  • kilo, milli, centi

Calculator Usage

  • Scientific Notation (EE button)

  • Order of operations

Scientific Notation

  • Example: 3.4 \times 10^4 = 34000

Significant Digits

  • Donā€™t round until the end of calculations to maintain accuracy.

Scientific Method

  • Problem

  • Hypothesis

  • Materials

  • Procedure

  • Observations

  • Conclusions

Variables

  • Manipulated (Independent): The variable you change.

  • Responding (Dependent): The variable that is affected by the change.

  • Fixed (Controlled)(Constants): Variables kept the same.

  • Control: A standard for comparison in an experiment.

Graphing

  • Choose the correct graph type (Bar or Line).

  • Title.

  • Label axes with units indicated in brackets.

  • Proper & equal scale of numbers on axes

  • Points plotted accurately.

  • Line of best fit (if applicable).

  • Legend (if required).

Reading a Graph

  • Calculate slope.

  • Interpret trends (Rising?, Falling?, Horizontal?).

  • Understand what the slope represents.

  • Understand the meaning of the area under the graph.

  • Examples:-

    • Graph 1

    • Graph 2

    • Graph 3

    • Graph 4

Physics Formulas

  • v = \frac{\Delta d}{\Delta t} = \frac{d2 - d1}{t2 - t1}

  • a = \frac{\Delta v}{\Delta t} = \frac{v2 - v1}{t2 - t1}

  • F = ma = m \cdot \frac{v}{t}

  • W = Fd = mad = m \cdot \frac{v}{t} \cdot d

  • E_p = mgh

  • E_k = \frac{1}{2} mv^2

  • Em = Ep + E_k

  • Efficiency = \frac{Useful \ work \ out}{Energy \ in} \times 100

Distance vs. Time Graphs

  • Slope of a horizontal line (red line): 0 m/s (no movement)

  • Difference between lines:-

    • Blue: Fast

    • Purple: Slow

  • Orange line: Movement toward you

  • Pink line: Acceleration

Scalar vs. Vector Quantities

  • Scalar: Only magnitude (how much).- Example: Distance (4m), Speed (10m/s)

  • Vector: Magnitude and direction.- Example: Displacement (4m [N]), Velocity (10m/s [E])

Velocity vs. Time Graphs

  • Slope of a horizontal line (red line): 0 m/sĀ² (constant speed)

  • Purple line: Changing speed = acceleration

  • Orange line: Changing speed = deceleration

  • Area under the red line: Area = lw = vt = distance (m)

Force

  • Formula: Force = Mass (kg) x Acceleration (m/sĀ²)

  • Units: kgā€¢m/sĀ² = Newtons (N)

  • More massive objects apply more force.

  • Faster acceleration requires more force.

  • Force of Gravity = Mass (kg) x Acceleration due to gravity (m/sĀ²) = Mass (kg) x 9.81 m/sĀ² (on Earth)

Work

  • Formula: Work = Force (N) x Distance (m)

  • Units: Nā€¢m = kgā€¢mĀ²/sĀ² = Joules (J) => UNIT OF ENERGY

  • Rules for Work:

    1. There must be movement.

    2. There must be force applied.

    3. Force and distance moved must be in the same direction.

  • The change in energy is equal to the work done: \Delta E = W

Forms of Energy

  • Chemical, Electrical, Nuclear, Solar, Motion, Heat

Gravitational Potential Energy

  • E_p = mgh

    • m = mass (kg)

    • g = acceleration of gravity (9.81 m/sĀ²)

    • h = height above ground (m)

  • Weight (W) = mg = the FORCE of gravity pulling on you

Elastic Potential Energy

  • Can be calculated by the work put into stretching the elastic (Work = Force x Distance)

Kinetic Energy

  • E_k = \frac{1}{2} mv^2

    • m = mass (kg)

    • v = velocity (m/s)

  • Speed has a greater effect on the amount of kinetic energy than does mass (because it is squared).

  • Kinetic energy can be converted to potential energy and vice versa.-

    • Example: If shooting an arrow straight up: Ep (at top) = Ek (at bottom)

Mechanical Energy

  • Em = Ep + E_k = mgh + \frac{1}{2} mv^2

  • Objects (i.e., a thrown ball) may have both movement and height (potential energy) at the same time.

  • Total energy is always conserved. This is the Law of Conservation of Energy (The First Law of Thermodynamics).

Systems

  • Open, Closed, and Isolated Systems:-

    • Open = Exchange matter and energy

    • Closed = Exchange energy; not matter

    • Isolated = Donā€™t exchange either

Second Law of Thermodynamics

  • Heat moves from hot to cold things.

Efficiency

  • Efficiency = \frac{Useful \ Energy \ (Work) \ Out}{Total \ Energy \ (Work) \ In}

  • Machines and systems can never be at or over 100% efficient.

  • Some energy is always lost as heat energy (not useful).