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/s², km/h²

• Force (F): Newtons (N) = kg•m/s²

• Work (W): Joules (J) = kg•m²/s²

• Potential Energy (Eₚ): Joules (J)

• Kinetic Energy (Eₖ): Joules (J)

• Mechanical Energy (Eₘ): 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

• Don’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/s² (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/s²)

• Units: kg•m/s² = Newtons (N)

• More massive objects apply more force.

• Faster acceleration requires more force.

• Force of Gravity = Mass (kg) x Acceleration due to gravity (m/s²) = Mass (kg) x 9.81 m/s² (on Earth)

Work

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

• Units: N•m = kg•m²/s² = 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/s²)

  • 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 = Don’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).