PHY 101 (100 LEVEL) First Semester 20242025

Physics Overview

Physics is the scientific study of the natural world, focusing on matter, energy, and the fundamental laws governing the physical universe, particularly space and time.

Space and Time

• Space: A three-dimensional continuum containing positions and directions. It describes the extent in which entities exist and maintain physical relationships.

• Time: Defined as the elapsed duration of events, considered absolute and one-dimensional. It flows at a consistent rate everywhere.

Units of Measurement

Units serve as standards for measuring physical quantities. The most widely used is the International System of Units (SI), which includes:

• Length: Meter (m)

• Mass: Kilogram (kg)

• Time: Second (s)

• Temperature: Kelvin (K)

• Electric Current: Ampere (A)

• Amount of Substance: Mole (mol)

• Luminous Intensity: Candela (cd)

Derived Units

Derived units are expressed in terms of base units. Examples include:

• Newton (N): Unit of force (N = kg·m/s²)

• Joule (J): Unit of energy/work done (J = kg·m²/s²)

• Watt (W): Unit of power (W = J/s)

Dimensions in Physics

Dimensions describe fundamental characteristics of physical quantities:

• Length (L): Measurable in meters (e.g., width, breadth, height).

• Mass (M): Measurable in kilograms.

• Time (T): Measurable in seconds.

• Temperature (Θ): Measurable in Kelvin.

• Electric Current (I): Measured in Amperes.

• Luminous Intensity (J): Measured in Candelas.

Dimensional Analysis

This process analyzes the dimensions of physical quantities to reveal their relationships, useful in validating and deriving equations.

Key Equations

• Speed: v = distance/time

• Acceleration: a = change in velocity/change in time

a = (v - u)/t

• Force: F = mass × acceleration

• Energy: E = force × distance

• Pressure: P = force/area

Examples of Calculations

1. Acceleration Calculation:

   • A car accelerates from rest to a speed of 60 km/h in 10 seconds:

     • a = (60 km/h) × (1000 m/km) / (3600 s/h) = 16.67 m/s²

2. Final Velocity for Dropping Object:

   • An object dropped from a height of 100m, after 2 seconds, using g = 9.8 m/s²:

     • Final velocity: v² = u² + 2gs (where u = 0)

Relative Motion

Relative motion describes the motion of an object as observed from another moving reference frame. It includes concepts like relative velocity and acceleration, which can help solve collision problems.

Conservation Principles

Conservation principles pertain to preserving specific physical quantities during processes:

• Conservation of Energy

• Conservation of Momentum

• Conservation of Charge

Types of Collisions

• Elastic Collision: Both momentum and kinetic energy are conserved.

• Inelastic Collision: Momentum is conserved, but kinetic energy is not.

• Perfectly Inelastic Collision: Colliding bodies stick together.

Moment of Inertia

The moment of inertia (I) quantifies an object's resistance to angular acceleration. It is defined as:

• I = Σ mᵢrᵢ²Where mᵢ is mass and rᵢ is the perpendicular distance to the axis of rotation.

Common Shapes and their Moments of Inertia

1. Rod (at one end): I = (1/3)mL²

2. Rod (at center): I = (1/12)mL²

3. Disk: I = (1/2)mR²

4. Cylinder: I = (1/2)mR²

Precession and Gyroscopes

Precession is the phenomenon where a spinning object’s axis moves due to torque, illustrating the gyroscopic effect.

Gravitational Theory

Newton's law of gravitation describes the attractive force between two masses: F = G(m₁m₂)/r²Where G is the gravitational constant and r is the distance between the masses.

Gravitational Potential Energy

Potential energy in a gravitational field can be calculated based on the work done against gravity.U = -G(m₁m₂)/r This shows the energy varies inversely with the distance between two masses.