FORCES

Introduction

  • Good Afternoon

Puzzle Section

  • Word Search Puzzle available online (https://thewordsearch.com/puzzle/1807607/)

Physics Overview

  • Definition: Physics is the branch of science that deals with the structure of matter and interactions among the fundamental constituents of the universe.

Force

  • Definition: A force is a push or pull on an object resulting from its interaction with another object.

Newton's Laws of Motion

  • Concept: Newton refined Galileo's ideas and proposed laws of motion. He believed that frictional forces are necessary to stop a moving object, influencing the concept of motion.

Effects of Force on Motion

  1. Force can start motion:

    • Example: A push cart starts moving from rest.

  2. Force can stop motion:

    • Example: A push cart can be made to stop.

  3. Force can change direction:

    • Example: A push cart can turn to the left.

Measurement of Force

  • Vector Quantity: Force is a vector quantity and is measured in Newtons (N).

  • Formula: F = ma

    • F = Force (N)

    • m = mass (kg)

    • a = acceleration (m/s²)

    • 1 Newton = 1 kg⋅m/s²

Net Force

  • Net Force: The sum of all forces acting on an object.

  • Balanced Force: No change of motion.

  • Unbalanced Force: Causes a change in motion.

Types of Forces

Balanced vs. Unbalanced Forces

  • Balanced forces (e.g., 300 N vs. 300 N) keep motion unchanged.

  • Unbalanced forces (e.g., 400 N vs. 300 N) result in a change in motion.

Contact Forces

  • Definition: Forces that require physical contact.

  • Types of Contact Forces:

    • Applied Force: Exerted by one object on another.

    • Normal Force: Support force exerted upon an object in contact with a stable surface.

    • Frictional Force: Occurs when two surfaces rub against each other.

    • Air Resistance: A form of friction acting on objects moving through air.

    • Tensional Force: Force transmitted through a string or rope.

    • Spring Force: Force exerted by a compressed or stretched spring.

Frictional Force

  • Static Friction: Friction that prevents motion.

  • Kinetic Friction: Friction acting on moving objects, can be:

    • Sliding Friction: Resistance experienced by an object sliding over another.

    • Rolling Friction: Resistance when an object rolls over a surface.

  • Characteristics of Friction:

    • Acts along the surface of contact opposite direction of motion.

    • Proportional to the normal force.

    • Nature of surface affects friction.

Factors Affecting Friction

  1. Nature of the materials.

  2. Degree of materials pressed together (Normal Force).

Non-Contact Forces

  • Definition: Forces that do not require physical contact.

  • Types of Non-Contact Forces:

    • Force of Gravity: Attracts objects towards massive bodies like Earth.

    • Electrical Force: Exists between charges, can be attractive or repulsive.

    • Magnetic Force: Exists in magnets, causing attraction or repulsion.

Free-Body Diagram (FBD)

  • Definition: A diagram showing all known and unknown forces acting on an object, indicating their magnitude and direction.

Assumptions in FBD

  1. Pulleys are assumed to be frictionless.

  2. Pulleys are assumed to be weightless.

  3. Ropes, cables, and wires are assumed to be weightless.