Chapter 2: Newton's Laws and Motion

Types of Forces and Motion

This section introduces the concept of force, types of motion, and Newton's First Law, which forms the foundation for understanding classical mechanics.

• Force: A push or pull on an object, measured in newtons (N).

• Newton's First Law of Motion (Law of Inertia): An object at rest stays at rest, and an object in motion stays in motion unless acted upon by a net force.

• Inertia: The resistance of an object to changes in its state of motion. The greater the mass, the greater the inertia.

• Examples of Inertia:

  • Seatbelts and headrests in a car

  • Tablecloth trick

  • Embroidery hoop with pennies stacked on top

• Net Force: The sum of all forces acting on an object. Units: newtons (N).

Scalar vs. Vector Quantities

Physical quantities are classified as scalars or vectors, which is essential for understanding motion and force.

• Scalar: Has only magnitude (e.g., speed, mass, time).

• Vector: Has both magnitude and direction (e.g., velocity, force, acceleration).

• Adding Vectors:

  • Tip-to-tail method

  • Parallelogram method

Mechanical Equilibrium and Force Vectors

An object is in mechanical equilibrium when the net force acting on it is zero.

• Support Force: An upward force that balances the force of gravity.

• Equilibrium of Moving Things: Objects moving at constant velocity are in dynamic equilibrium.

Chapter 3: Kinematics – Speed, Velocity, and Acceleration

Speed

Speed is a measure of how fast an object moves, defined as the distance traveled per unit time.

• Average Speed:

• Units: meters per second (m/s)

• Instantaneous Speed: The speed at a specific instant, measured by a speedometer.

Velocity

Velocity is a vector quantity that includes both speed and direction.

• Formula:

• Constant velocity means both speed and direction are constant.

• Changing velocity can be due to changes in speed, direction, or both.

Acceleration

Acceleration is the rate at which velocity changes with time and requires both magnitude and direction.

• Formula:

• Units: meters per second squared (m/s2)

• Acceleration can be positive (speeding up) or negative (slowing down).

Free-Fall Motion

Objects in free fall experience acceleration due to gravity, with air resistance neglected.

• Acceleration due to gravity: (approximate value)

• Velocity and acceleration can be in opposite directions (e.g., braking a car).

Graphs of Motion

Graphs are useful for visualizing motion and understanding relationships between position, velocity, and acceleration.

• Position vs. Time Graph: Slope represents velocity.

• Velocity vs. Time Graph: Slope represents acceleration.

Chapter 4: Newton's Second Law of Motion

Force and Acceleration

Newton's Second Law relates the net force acting on an object to its acceleration and mass.

• Formula:

• Acceleration is directly proportional to net force and inversely proportional to mass.

• Direction of force is the same as the direction of acceleration.

Friction

Friction is a force that resists the relative motion of objects in contact.

• Types of Friction:

  • Static Friction: Prevents motion until a threshold force is reached.

  • Kinetic Friction: Acts during motion; usually less than static friction.

• Friction occurs in solids, liquids, and gases (air resistance).

• Air resistance increases with speed and surface area.

Mass and Weight

Mass is a measure of the amount of matter in an object, while weight is the force of gravity acting on that mass.

• Mass: Measured in kilograms (kg).

• Weight:

• Greater mass means greater inertia.

• For a given force, acceleration is inversely proportional to mass:

Free Fall and Acceleration Due to Gravity

When gravity is the only force acting, all objects accelerate at the same rate regardless of mass (neglecting air resistance).

• Formula:

• Acceleration due to gravity is independent of mass.

• Inertia resists changes in motion, but gravity acts equally on all masses.

Non-Free Fall and Air Resistance

When air resistance is significant, it affects the acceleration and terminal speed of falling objects.

• Air resistance depends on size, shape, and speed.

• Terminal speed is the fastest speed an object can reach when falling through air.

• At terminal speed, the upward force of air resistance equals the downward force of gravity ().

• Acceleration decreases as an object approaches terminal speed.

Terminal Speeds of Various Objects

Summary Table: Key Concepts

Additional info: Some explanations and table entries have been expanded for clarity and completeness, based on standard introductory physics curriculum.