Basic Physics Lecture Notes PDF

Menoufia University Faculty of Applied Health Science Technology OFRPY102: Basic Physics CH 2 NEWTON’S LAWS OF MOTION Course Lecturer DR. Mohamed Tharwat Lecturer in Engineering Physics Faculty of Electronic Engineering...

Menoufia University Faculty of Applied Health Science Technology OFRPY102: Basic Physics CH 2 NEWTON’S LAWS OF MOTION Course Lecturer DR. Mohamed Tharwat Lecturer in Engineering Physics Faculty of Electronic Engineering 44 Level_1 Basic Physics Session Policy Physics (2) 45 Dr. Mohamed Tharwat Level_1 Basic Physics OUTLINE 1. INTRODUCTION 2. FORCE AND MASS 3. NEWTON’S FIRST LAW OF MOTION 4. NEWTON’S SECOND LAW OF MOTION 5. NEWTON'S THIRD LAW OF MOTION 6. SOLVED PROBLEMS 46 Dr. Mohamed Tharwat Level_1 Basic Physics 1. INTRODUCTION Newton's laws of motion are fundamental principles in classical mechanics that describe the relationship between force, mass, and acceleration. These laws provide the foundation for understanding the motion of objects in our everyday world. 47 Dr. Mohamed Tharwat Level_1 Basic Physics 2. FORCE AND MASS  Force is defined as a push or pull upon an object resulting from its interaction with another object. It causes the object to accelerate, decelerate, change direction, or change shape. Force is a vector quantity, meaning it has both magnitude (strength) and direction. 48 Dr. Mohamed Tharwat Level_1 Basic Physics 2. FORCE AND MASS  Force and mass are two Table 2.1: Typical Masses in Kilograms (kg) fundamental concepts in physics Object Mass (Kg) that are closely intertwined. A list of Earth 5.97 x 1024 Space shuttle 2,000,000 typical masses is given in Table 2-1. Blue whale (largest animal 105,000 on Earth) Whale shark (largest fish) 18,000 Elephant (largest land 5400 animal) Automobile 1200 Human (adult) 70 Gallon of milk 3.9 Quart of milk 1.0 Baseball 0.145 Honeybee 0.00015 49 Bacterium 10-15 Tharwat Dr. Mohamed Level_1 Basic Physics 2. FORCE AND MASS 50 Dr. Mohamed Tharwat Level_1 Basic Physics 3. NEWTON’S FIRST LAW OF MOTION Newton's First Law of Motion, also known as the Law of Inertia, states that: "An object at rest will remain at rest, and an object in motion will continue to move in a straight line at a constant speed unless acted upon by an unbalanced force." 51 Dr. Mohamed Tharwat Level_1 Basic Physics 3. NEWTON’S FIRST LAW OF MOTION  This means that an object will maintain its current state of motion unless a force changes it. If an object is at rest, it will stay at rest unless a force pushes or pulls it. If an object is moving, it will continue to move in the same direction and at the same speed unless a force slows it down, speeds it up, or changes its direction. 52 Dr. Mohamed Tharwat Level_1 Basic Physics 3. NEWTON’S FIRST LAW OF MOTION When a body is either at rest or moving with constant velocity (in a straight line with constant speed), we say that the body is in equilibrium. For a body to be in equilibrium, it must be acted on by no forces, or by several forces such that their vector sum—that is, the net force—is zero: 53 Dr. Mohamed Tharwat Level_1 Basic Physics 3. Newton’s Second Law of Motion Newton's Second Law of Motion states that: The acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass. 54 Dr. Mohamed Tharwat Level_1 Basic Physics 3. Newton’s Second Law of Motion  This means that the greater the force applied to an object, the greater its acceleration will be. Additionally, the smaller the object's mass, the easier it is to accelerate it. Mathematically, this relationship can be expressed as: 55 Dr. Mohamed Tharwat Level_1 Basic Physics 3. Newton’s Second Law of Motion This equation is a fundamental principle of classical mechanics and is used to analyze the motion of objects in various situations. For example, it can be used to calculate the force required to accelerate a car or to determine the acceleration of a falling object. 56 Dr. Mohamed Tharwat Level_1 Basic Physics 3. Newton’s Second Law of Motion Example 2.1 The net force acting on a Cessna 172 airplane has a magnitude of 1900 N and points in the positive x direction. If the plane has a mass of 860 kg, what is its acceleration? solution Only x components are involved in this system, so we use the x component of Newton’s second law, , solving this equation for the acceleration gives 57 Dr. Mohamed Tharwat Level_1 Basic Physics 3. Newton’s Second Law of Motion Example 2.2 A 1000 kg car accelerates from rest to 25 m/s in 10 seconds. What is the net force acting on the car? Solution Given: mass (m) = 1000 kg, initial velocity (u) = 0 m/s, final velocity (v) = 25 m/s, time (t) = 10 s Acceleration (a) = (v - u) / t = (25 m/s - 0 m/s) / 10 s = 2.5 m/s² Force (F) = ma = 1000 kg * 2.5 m/s² = 2500 N 58 Dr. Mohamed Tharwat Level_1 Basic Physics 3. Newton’s Second Law of Motion Example 2.3 A 1000 kg car is traveling at a constant velocity of 20 m/s. What is the net force acting on the car? Solution If the car is traveling at a constant velocity, its acceleration is 0 m/s². From Newton's second law, F = ma = 1000 kg * 0 m/s² = 0 N 59 Dr. Mohamed Tharwat Level_1 Basic Physics 3. Newton's Third Law of Motion Newton's Third Law of Motion, also known as the Law of Action and Reaction, states that: For every action, there is an equal and opposite reaction. 60 Dr. Mohamed Tharwat Level_1 Basic Physics 3. Newton's Third Law of Motion Example 2.4 A rocket expels 1000 kg of gas per second at a speed of 2000 m/s. What is the thrust force exerted on the rocket? Solution The thrust force is equal to the rate of change of momentum of the expelled gas. Thrust force = (mass of gas expelled per second) * (velocity of expelled gas) Thrust force = 1000 kg/s * 2000 m/s = 2,000,000 N 61 Dr. Mohamed Tharwat Credited Hours Programs Level_0 Questions and Discussion Dr. Mohamed Tharwat Credited Hours Programs Level_0 The End Good Luck See You in Next Lecture ISA With my Best Wishes Dr. Mohamed Tharwat Dr. Mohamed Tharwat