🍏Principles of Physics I Unit 1 – Physics Foundations: Math and Concepts

Key Mathematical Tools

• Algebra provides the foundation for manipulating equations and solving for unknown variables in physics problems
  • Includes techniques like isolating variables, factoring, and simplifying expressions
  • Essential for rearranging formulas to solve for specific quantities (velocity, acceleration, force)
• Trigonometry is crucial for analyzing vectors, angles, and motion in two or more dimensions
  • Sine, cosine, and tangent functions relate angles to the lengths of triangle sides
  • Used to resolve vectors into components and calculate resultant vectors
• Calculus allows for the study of change and motion in physics
  • Derivatives measure instantaneous rates of change (velocity, acceleration)
  • Integrals calculate quantities over continuous domains (work, displacement)
• Geometry concepts are applied to analyze shapes, areas, and volumes in physics scenarios
  • Pythagorean theorem calculates distances and magnitudes of vectors
  • Area and volume formulas are used in problems involving density, pressure, and fluid dynamics
• Graphing skills help visualize and interpret physical relationships between variables
  • Slope of a graph represents the rate of change (velocity on a position-time graph)
  • Area under a curve can represent displacement, work, or other cumulative quantities

Fundamental Physics Concepts

• Matter is anything that occupies space and has mass
  • Composed of atoms, which consist of protons, neutrons, and electrons
  • Exists in various states (solid, liquid, gas, plasma) depending on temperature and pressure
• Energy is the capacity to do work or cause change
  • Comes in different forms (kinetic, potential, thermal, electrical, nuclear)
  • Can be converted from one form to another, but cannot be created or destroyed (conservation of energy)
• Force is an interaction that can change an object's motion or shape
  • Measured in newtons (N) and represented as a vector quantity
  • Examples include gravity, friction, tension, and normal force
• Fields describe the influence of forces over a region of space
  • Gravitational fields represent the force of gravity around massive objects
  • Electric fields depict the force experienced by charged particles
  • Magnetic fields illustrate the force on moving charges or magnetic materials
• Waves are oscillations that transfer energy through a medium or space
  • Characterized by wavelength, frequency, and amplitude
  • Examples include sound waves, light waves, and water waves

Units and Measurements

• SI units (International System of Units) provide a standardized way to express physical quantities
  • Fundamental units include meter (m) for length, kilogram (kg) for mass, second (s) for time, and others
  • Derived units are combinations of fundamental units (joule (J) for energy, newton (N) for force)
• Prefixes are used to indicate orders of magnitude for SI units
  • Micro- ($\mu$) represents 10^-6, milli- (m) is 10^-3, kilo- (k) is 10^3, mega- (M) is 10^6
  • Helps express very large or small quantities concisely (nanometer, gigawatt)
• Dimensional analysis is a problem-solving technique that uses units to guide calculations
  • Ensures the units in an equation are consistent and cancel out correctly
  • Helps identify the appropriate formula or relationship to use based on the given units
• Significant figures indicate the precision and uncertainty of a measured value
  • Determined by the least precise measurement used in a calculation
  • Proper reporting of results should include the appropriate number of significant figures
• Scientific notation expresses very large or small numbers concisely
  • Consists of a number between 1 and 10 multiplied by a power of 10
  • Useful for calculations involving astronomical distances or atomic-scale quantities

Vectors and Scalars

• Scalars are quantities that have only magnitude, such as mass, temperature, and time
  • Can be added, subtracted, multiplied, or divided using ordinary arithmetic
  • Example: A cup of coffee has a temperature of 70°C
• Vectors are quantities that have both magnitude and direction, like displacement, velocity, and force
  • Represented graphically as arrows, with the length indicating magnitude and the arrow showing direction
  • Example: A car travels 50 km/h due east
• Vector addition combines two or more vectors to find the resultant vector
  • Graphically, vectors are placed head-to-tail, and the resultant connects the tail of the first to the head of the last
  • Analytically, vector components are added separately to find the resultant components
• Vector subtraction is the addition of a vector and the negative of another vector
  • The negative of a vector has the same magnitude but opposite direction
  • Graphically, the negative vector is placed tail-to-tail with the original vector
• Scalar multiplication changes the magnitude of a vector without altering its direction
  • Multiplying a vector by a positive scalar lengthens the vector
  • Multiplying a vector by a negative scalar reverses the vector's direction

Motion in One Dimension

• Position is the location of an object relative to a chosen reference point
  • Represented by a coordinate system, such as the x-axis for one-dimensional motion
  • Change in position is called displacement, a vector quantity
• Velocity is the rate of change of position with respect to time
  • Calculated as displacement divided by time interval: $v = \frac{\Delta x}{\Delta t}$
  • Positive velocity indicates motion in the positive direction, while negative velocity is motion in the negative direction
• Acceleration is the rate of change of velocity with respect to time
  • Calculated as change in velocity divided by time interval: $a = \frac{\Delta v}{\Delta t}$
  • Positive acceleration is an increase in velocity, while negative acceleration (deceleration) is a decrease in velocity
• Motion graphs visually represent an object's position, velocity, or acceleration over time
  • Position-time graphs have position on the vertical axis and time on the horizontal axis
    • Slope of the graph represents velocity
  • Velocity-time graphs have velocity on the vertical axis and time on the horizontal axis
    • Slope of the graph represents acceleration
    • Area under the graph represents displacement
• Kinematic equations describe motion using position, velocity, acceleration, and time variables
  • $x = x_0 + v_0t + \frac{1}{2}at^2$ (position as a function of time)
  • $v = v_0 + at$ (velocity as a function of time)
  • $v^2 = v_0^2 + 2a(x - x_0)$ (velocity as a function of position)

Forces and Newton's Laws

• Newton's first law (law of inertia) states that an object at rest stays at rest, and an object in motion stays in motion with constant velocity, unless acted upon by an unbalanced force
  • Inertia is the resistance of an object to changes in its motion
  • Objects with greater mass have greater inertia and require larger forces to change their motion
• Newton's second law relates the net force acting on an object to its mass and acceleration: $\vec{F}_{net} = m\vec{a}$
  • The acceleration of an object is directly proportional to the net force and inversely proportional to its mass
  • In SI units, force is measured in newtons (N), mass in kilograms (kg), and acceleration in meters per second squared (m/s²)
• Newton's third law states that for every action force, there is an equal and opposite reaction force
  • Action-reaction force pairs act on different objects and do not cancel each other out
  • Examples include the force of a foot pushing against the ground (action) and the ground pushing back (reaction)
• Free body diagrams visually represent all the forces acting on an object
  • Each force is drawn as a vector arrow, with the tail at the object's center of mass
  • Helps identify the net force and apply Newton's second law to solve for acceleration or other quantities
• Friction is a force that opposes the relative motion between two surfaces in contact
  • Static friction prevents an object from starting to move, up to a certain maximum force
  • Kinetic friction acts on objects that are already in motion, typically less than static friction
  • Coefficient of friction ($\mu$) is a dimensionless number that depends on the materials in contact

Energy and Work

• Energy is the capacity to do work or cause change
  • Measured in joules (J) in SI units
  • Can be converted from one form to another, but cannot be created or destroyed (conservation of energy)
• Kinetic energy (KE) is the energy an object possesses due to its motion
  • Calculated as $KE = \frac{1}{2}mv^2$, where $m$ is mass and $v$ is velocity
  • Depends on both the mass and speed of the object
• Potential energy (PE) is the energy an object has due to its position or configuration
  • Gravitational PE depends on an object's mass, height, and the strength of the gravitational field: $PE_g = mgh$
  • Elastic PE is stored in deformed materials, such as compressed springs: $PE_e = \frac{1}{2}kx^2$
• Work is the transfer of energy by a force acting over a distance
  • Calculated as the dot product of force and displacement vectors: $W = \vec{F} \cdot \vec{d}$
  • Measured in joules (J), the same unit as energy
  • Work done by a force can change an object's kinetic or potential energy
• Power is the rate at which work is done or energy is transferred
  • Calculated as work divided by time: $P = \frac{W}{\Delta t}$
  • Measured in watts (W), equivalent to joules per second (J/s)
• Conservation of mechanical energy states that the total mechanical energy (KE + PE) in a closed system remains constant
  • Energy can be converted between kinetic and potential forms, but the sum remains the same
  • Applies to systems with conservative forces, such as gravity and elastic forces

Problem-Solving Strategies

• Identify the given information and the quantity you are asked to find
  • Carefully read the problem statement and list the known variables and their values
  • Determine the target variable and the appropriate units for the answer
• Visualize the problem situation with diagrams or sketches
  • Draw a simple sketch of the physical scenario, including relevant objects and distances
  • For problems involving forces, create a free body diagram to represent the forces acting on the object
• Break down complex problems into smaller, manageable steps
  • Identify the intermediate quantities you need to calculate before reaching the final answer
  • Solve for one unknown variable at a time, using the given information and relevant equations
• Select the appropriate equations or principles to solve the problem
  • Based on the given variables and the quantity you are asked to find, choose the relevant equations
  • Consider the assumptions or conditions required for each equation to be valid
• Perform the necessary calculations, following mathematical rules and maintaining unit consistency
  • Substitute the known values into the selected equations and solve for the unknown variable
  • Carry out algebraic manipulations and simplifications carefully, showing your work step by step
• Evaluate the reasonableness of your answer
  • Check if the answer has the correct units and a reasonable order of magnitude
  • Consider whether the answer makes sense in the context of the problem situation
• Reflect on the problem-solving process and learn from your mistakes
  • If your answer is incorrect, review your solution steps to identify any errors or misconceptions
  • Analyze the problem-solving strategies that worked well and those that need improvement