General Physics (PHYS 101) Lecture Notes PDF

Physics Department General Physics (PHYS 101) Updated By: Dr. Najah Alwadie 1 2024 - 1446 [email protected]  Physics...

Physics Department General Physics (PHYS 101) Updated By: Dr. Najah Alwadie 1 2024 - 1446 [email protected]  Physics Department Lecture 3: Lows of Motion Chapter 5 Updated By: Dr. Najah Alwadie 2  Physics Department Learning Outcomes …In this chapter, you’ll learn 1. The Concept of Force. 2. Newton’s First Law and Inertial Frames. 3. Mass. 4. Newton’s Second Law..Newton’s Law of Universal Gravitation.5 6. Newton’s Third Law. 3  Introduction We’ve seen how to use kinematics to describe motion in one dimension. But what causes objects to move the way that they do? The answer takes us into the subject of dynamics, the relationship of motion to the forces that cause it. The principles of dynamics were clearly stated for the first time by Sir Isaac Newton, today we call them Newton’s laws of motion. Newton did not derive these laws, but rather deduced them from a multitude of experiments performed by other scientists.  Physics Department The Concept of Force contact forces field forces ?What are Some Properties of a Force  :There Are Four Common Types of Forces 1 2.. 3.4.  Physics Department The Vector Nature of Force 8  Physics Department ?? What is Zero Net Force The net force (or resultant force ) acting on an object is defined as the vector sum of all forces acting on the object. What happens when the net force on an object is zero ?!  Newton’s First Law and Inertial Frames Newton’s first law of motion, sometimes called the law of inertia, defines a special set of reference frames called :inertial frames. So, this law can be stated as follows.Such a reference frame is called an inertial frame of reference.In other words, when no force acts on an object, the acceleration of the object is zero.…………………………………… Also, from the first law, we can define force as 10  ?What is Inertia Inertia is the tendency of an object to resist changes in its velocity: whether in motion or motionless. ?What is Inertia.This law is the same reason why you should always wear your seatbelt  Physics Department Mass Mass is that property of an object that specifies how much resistance an object exhibits to changes in its velocity. The SI unit of mass is the ………………………….. Masses can be defined in terms of the accelerations produced by a given force acting on them: m1/m2 = a2/a1 How the acceleration of an object is determined by the object’s mass ?!  Physics Department Mass vs. Weight Mass and weight are two different quantities.  Weight is equal to the magnitude of the gravitational force exerted on the object.  Weight will vary with location.  On other planets, g will have an entirely different value than on the earth. : Ex. : Man whose weight is 1000 N on the earth has a mass of..…………… = m 14  Physics Department The Gravitational Force and Weight all objects are attracted to the Earth. The attractive force exerted by the Earth on an object is called the gravitational force Fg. This force is directed toward the center of the Earth, and its magnitude is called the weight of the object.  Newton's Second Law of Motion Newton’s second law: the net force on a body is equal to the product of the body’s mass and.its acceleration How the acceleration of an object is determined by the net force on the object and the object’s mass ?!.…………… The SI unit for force is  Systems of Units System of Units Force Mass Acceleration SI newton (N) kilogram (k g) meters per second squared cgs dyne (dyn) gram (g) centimeters per second squared British pound (lb) slug feet per second squared :Example Mike's car, which weighs 1,000 kg, is out of gas. Mike is trying to push the car to a gas station, and he makes the car go 0.05 m/s/s. Using Newton's Second Law, you can compute how much force Mike is applying to the.car  Physics Department Newton’s Law of Universal Gravitation where G is a constant, called ……………………………………………., that has been measured experimentally. Its value in SI units is G = 6.673 X 10 -11 N. m 2/k g 2  Physics Department Newton’s Third Law How the forces that two objects exert on each other are related ?! Reaction Action A pushes / pulls B. B pushes / pulls A.  Problems & Exercises 21  Physics Department Problem ( no.1 page 131 ) -1 Problem ( no. 3 Page 131 ) -2 3- What is the weight of a 200 kg object? 4- A woman exerts a force of 500 N straight up to lift a 35 kg basket. What is the acceleration of the basket? 22