1Lecture 5Dynamics ForceNewton’s Laws of MotionPhysics 111, Summer 2011, June 20, Lecture 5 SummaryAn object has oneor twocomponents of the initial velocity:along x(horizontal) direction and along y(vertical) direction.2A projectileis any object that is given an initial velocity and then follows a path determined by the horizontal and vertical motion (air resistance is important by can be ignored).Projectile motion is simultaneous motion in horizontal and vertical directions.An object has onenon-zero component of acceleration: along x(horizontal) direction: along y(vertical) direction.Equations for projectile motion,vertical component:Equation for projectile motion, horizontal component:0xv0yv0xagaygtvvyy0220gttvyyconstvvxx0tvxx0Physics 111, Summer 2011, June 20, Lecture 5 DynamicsKinematics:explains how objects move.Dynamics:explains how objects motion depends on forces acting on them.We use: distance, time, speed, velocity, and acceleration.We use: force, distance, time, speed, velocity, and acceleration.Force is the most important parameter describing dynamics.3An object changes its velocity, i.e. accelerates, if:- it moves faster, or- it moves slower.Why? Because some force is applied,Physics 111, Summer 2011, June 20, Lecture 5 Forceis a quantitative description of the interaction between two physical bodies, such as an object and its environment. Forceis any influence that causes a free body to undergo a change in speed, a change in direction, or a change in shape.What is Force?4Physics 111, Summer 2011, June 20, Lecture 5 The concept of forcewas originally defined by Isaac Newton in his three laws of motion. He explained gravity as an attractive force between bodies that possessed mass.DefinitionThe concept of force
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