Forces and Matter (EdExcel)

Introduction

Definition of Force

• A push or pull exerted on an object due to interaction with another object.

• It can cause an object to:

  • Change speed

  • Change direction

  • Change shape

Types of Forces

1. Contact Forces

   1. Forces that require physical interaction (e.g., friction, tension, normal force).

   2. Examples of Contact Forces:

      1. Friction

      2. Tension

      3. Normal force

      4. Air resistance

2. Non-Contact Forces

   1. Forces that act at a distance (e.g., gravity, magnetism, electrostatic force).

   2. Examples of Non-Contact Forces:

      1. Gravity

      2. Magnetic force

      3. Electrostatic force

Matter and Its Properties

• Matter is anything that has mass and occupies space.

• Properties of Matter:

  • Mass (amount of substance in an object)

  • Volume (amount of space it occupies)

  • Density (mass per unit volume, ρ=m/V​)

Forces Affecting Matter

• Gravity

  • Pulls matter towards Earth (e.g., objects falling).

• Elasticity

  • Matter can stretch and return to its shape (e.g., rubber bands).

• Pressure

  • Force applied over an area (e.g., fluid pressure).

Scalars and Vectors

• Scalars

  • Quantities with only magnitude (e.g., mass, distance, speed, energy).

• Vectors

  • Quantities with both magnitude and direction (e.g., force, displacement, velocity, acceleration).

Examples of Scalar and Vector quantities:

Distance and Displacement

• Distance

  • A scalar quantity (total path traveled).

• Displacement

  • A vector quantity (straight-line distance from start to end).

**Velocity

• Displacement per unit time (speed in a given direction).

Friction Force

• A resistive force that opposes motion between two surfaces in contact.

• Acts opposite to the direction of motion.

Application (Advantages) of Friction Force:

• Helps in lighting a matchstick.

• Prevents vehicles from sliding on roads (grip between tires and road).

Disadvantages of Friction Force:

• Causes wear and tear of machines.

• Leads to tire wear in vehicles.

Newton’s Laws of Motion

Newton’s First Law (Law of Inertia)

• An object remains at rest or moves with constant velocity unless acted upon by an external force.

Newton’s Second Law (Force & Acceleration)

• Force = Mass × Acceleration (F = ma)

Newton’s Third Law (Action-Reaction)

• For every action, there is an equal and opposite reaction.

Resultant Forces

• Net Force = 0 N (Balanced Forces)

  • An object remains at rest or moves at a constant speed.

• Net Force ≠ 0 N (Unbalanced Forces):

  • The object moves in the direction of the resultant force.

Momentum & Conservation of Momentum

• Momentum (p) = Mass × Velocity

• Law of Conservation of Momentum:

  • Total momentum before collision = Total momentum after collision (if no external force acts).