Chapter 4 Newton's Laws .pptx

MOHAMMED AL-MANA COLLEGE FOR MEDICAL SCIENCES Force and Newton’s Laws of Motion Chapter 4 MOHAMMED AL-MANA COLLEGE FOR MEDICAL SCIENCES LECTURE OBJECTIVES - At the end of the lecture, the student is going to identify Newton’s Laws. - At the end of the lecture, the student is going to apply Newto...

MOHAMMED AL-MANA COLLEGE FOR MEDICAL SCIENCES Force and Newton’s Laws of Motion Chapter 4 MOHAMMED AL-MANA COLLEGE FOR MEDICAL SCIENCES LECTURE OBJECTIVES - At the end of the lecture, the student is going to identify Newton’s Laws. - At the end of the lecture, the student is going to apply Newton’s law to solve problems. - At the end of the lecture, the student is going to interpret fundamental forces in nature . - At the end of the lecture, the student is going to solve frictional force problems. MOHAMMED AL-MANA COLLEGE FOR MEDICAL SCIENCES “The important thing is to never TODAY'S QUOTE stop questioning.” Albert Einestein MOHAMMED AL-MANA COLLEGE FOR MEDICAL SCIENCES LECTURE OUTLINE - The Concept of Force. - Newton’s First Law of Motion. - Newton’s Second Law of Motion. - Newton’s third Law of Motion. - Fundamental Forces in Nature. - Derived Forces. MOHAMMED AL-MANA COLLEGE FOR MEDICAL SCIENCES The Concept of Force Force is the influence that produces a change in the state of motion of a body, i.e., causes change in velocity or produces an acceleration. MOHAMMED AL-MANA COLLEGE FOR MEDICAL SCIENCES Which of these is a vector quantity? a) Speed b) Work c) Force d) All are vector quantities. MOHAMMED AL-MANA COLLEGE FOR MEDICAL SCIENCES Newton’s First Law of Motion Concept and Definition Concept and Definition Concept and Definition Any Body Continues at rest, or at The tendency of a body to maintain The more mass of a body, the more constant velocity(Constant Speed its state of motion is called inertia. is its inertia. in a straight line) unless acted upon by a net external force. Newton’s first law is called the law of inertia MOHAMMED AL-MANA COLLEGE FOR MEDICAL SCIENCES Inertia is a________? a) Force like any other force. b) Special kind of force. c) Property of all matter. d) Concept opposite to force. MOHAMMED AL-MANA COLLEGE FOR MEDICAL SCIENCES OPEN DISCUSSION MOHAMMED AL-MANA COLLEGE FOR MEDICAL SCIENCES Group Work Read the following statements and determine whether or not they represent examples of Newton’s First Law Time 10 Min MOHAMMED AL-MANA COLLEGE FOR MEDICAL SCIENCES Group Work • • • • A stationary object with no outside force will not move. With no outside forces, a moving object will stop. An object at rest stays at rest. An object in motion stays in motion. MOHAMMED AL-MANA COLLEGE FOR MEDICAL SCIENCES A pair of objects initially travel in the same direction. The lower object is subject to a force and its motion then deviates from a straight line while the force acts on it, but continuous on in a new straight line after the force ceases to act MOHAMMED AL-MANA COLLEGE FOR MEDICAL SCIENCES Newton’s Second Law of Motion Concept and Definition Concept and Definition Concept and Definition The net external force acting on a body is directly proportional to the acceleration produced in it. The acceleration a is proportional to the force F applied, and the constant of proportionality is the mass m. Mass is the resistance of a body to accelerate. It is determined by the amount of material of which the body consists. F=ma MOHAMMED AL-MANA COLLEGE FOR MEDICAL SCIENCES Newton’s Second Law of Motion When force of magnitude F is applied to an object of mass m, the object undergoes an acceleration of magnitude a MOHAMMED AL-MANA COLLEGE FOR MEDICAL SCIENCES Newton’s Second Law of Motion What would happen if the mass were twice as large? F 2m ?? MOHAMMED AL-MANA COLLEGE FOR MEDICAL SCIENCES Newton’s Second Law of Motion What would happen if the Force were twice as large? 2F m ?? MOHAMMED AL-MANA COLLEGE FOR MEDICAL SCIENCES Newton’s Second Law of Motion What would happen if the Force were twice as large? 2F m ?? MOHAMMED AL-MANA COLLEGE FOR MEDICAL SCIENCES Think -Pair -Share Read the following questions, think about them and pair the answer with your friends. Time 15 Min MOHAMMED AL-MANA COLLEGE FOR MEDICAL SCIENCES 1) How much force will a tennis racket need to exert on a tennis ball, with a mass of 0.67 kg, to make it accelerate at a rate of 5,600 m/s2? 2) A force of 250 N is applied to an object that accelerates at a rate of 5 m/sec2. What is the mass of the object? 3) You are pushing a friend on a sled. You push with a force of 20 N. Your friend and the sled together have a mass of 60 kg. Ignoring friction, what is the acceleration of your friend on the sled? MOHAMMED AL-MANA COLLEGE FOR MEDICAL SCIENCES Newton’s Second Law of Motion Weight and Mass: Any body of mass (m ) near the surface of the Earth experiences a downward force proportional to the acceleration due to gravity (g ), this force is referred to as weight. The weight is thus W = mg MOHAMMED AL-MANA COLLEGE FOR MEDICAL SCIENCES Think -Pair -Share Read the following questions, think about them and pair the answer with your friends. Time 5 Min MOHAMMED AL-MANA COLLEGE FOR MEDICAL SCIENCES ▪ If an object mass =30 Kg on the Earth, what would be it's weight on Earth? ▪ A man weighs 800 N. What is his mass in kilograms? MOHAMMED AL-MANA COLLEGE FOR MEDICAL SCIENCES Newton’s Third Law of Motion Concept and Definition To every action there is an equal and opposite reaction. Concept and Definition Concept and Definition This means that when one body exerts a force on a second body, the second body exerts an equal and opposite force on the first body. Forces act in pairs, and each force acts between a pair of objects. These pairs of forces are referred to as actionreaction pairs. Newton’s third law is called the Law of Action Reaction. MOHAMMED AL-MANA COLLEGE FOR MEDICAL SCIENCES Three examples of action- reaction pairs. The gravitational force between the Earth and the Moon, the downward contact force a block exerts on a surface and the upwards support force the surface exerts on the block, and a person pushing against a wall. MOHAMMED AL-MANA COLLEGE FOR MEDICAL SCIENCES Fundamental Forces in Nature Electromagnetic forces: holds atoms and molecules together: electron/proton Gravitational forces: responsible for the movement of planets around stars, stars in galaxies....The Earth’s gravity force produces weight and keeps us close to the earth’s surface. Strong forces: responsible for the stability of nucleus. Weak forces: responsible for beta particle emission from radioactive nuclei. MOHAMMED AL-MANA COLLEGE FOR MEDICAL SCIENCES Derived Forces 1. Tension ? The force that exists in the body of a flexible cable when forces are applied in opposite directions. ? The muscle fibers in human body behave like cables under tension MOHAMMED AL-MANA COLLEGE FOR MEDICAL SCIENCES Derived Forces 2. Normal Force When a block is kept on a horizontal surface the normal reaction and weight are equal and opposite. N = W = mg MOHAMMED AL-MANA COLLEGE FOR MEDICAL SCIENCES Derived Forces 3. Friction: Frictional force opposes relative motion between two surfaces. There are two kinds of friction: static and kinetic. MOHAMMED AL-MANA COLLEGE FOR MEDICAL SCIENCES Friction Concept and Definition Concept and Definition Concept and Definition Static friction- the force you must overcome to get an object sliding. Sliding (kinetic) friction- the force of friction that exists as one surface slides past another. Frictionstatic > Frictionsliding because of inertia. MOHAMMED AL-MANA COLLEGE FOR MEDICAL SCIENCES Measuring Frictional Force Concept and Definition Concept and Definition The frictional force (Ff ) is proportional to normal reaction (N ). The constant of proportionality is the coefficient of friction: Equation Ff = μN MOHAMMED AL-MANA COLLEGE FOR MEDICAL SCIENCES Group Work Work in group of 3 to 4 students. Read the following questions and find the answer. Time 5 Min MOHAMMED AL-MANA COLLEGE FOR MEDICAL SCIENCES • What is the force of friction between a block of ice that weighs 950 N and the ground if μ = 0.12? • A desk has a mass of 17.5 kilograms. If the coefficient of static friction between the desk and the floor is 0.28, what force must be used to move the desk from rest? MOHAMMED AL-MANA COLLEGE FOR MEDICAL SCIENCES QUESTIONS & ANSWERS MOHAMMED AL-MANA COLLEGE FOR MEDICAL SCIENCES THANK YOU CONTACT INFORMATION E-MAIL: [email protected] Office Hours: 08:00 - 04:00