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Unformatted text preview: Lecture #6 Part #1 NEWTON ` S LAWS OF MOTION, EQUATIONS OF MOTION, & EQUATIONS OF MOTION FOR A SYSTEM OF PARTICLES Today ` s Objectives : Students will be able to: 1. Write the equation of motion for an accelerating body. 2. Draw the freebody and kinetic diagrams for an accelerating body . InClass Activities : • Reading Quiz • Applications • Newton ` s Laws of Motion • Newton ` s Law of Gravitational Attraction • Equation of Motion For A Particle or System of Particles • Concept Quiz • Group Problem Solving • Attention Quiz READING QUIZ 1. Newton ` s second law can be written in mathematical form as Σ F = m a . Within the summation of forces, Σ F , ________ are(is) not included. A) external forces B) weight C) internal forces D) All of the above. 2. The equation of motion for a system of nparticles can be written as Σ F i = Σ m i a i = m a G , where a G indicates _______. A) summation of each particle ` s acceleration B) acceleration of the center of mass of the system C) acceleration of the largest particle D) READING QUIZ 1. Newton ` s second law can be written in mathematical form as Σ F = m a . Within the summation of forces, Σ F , ________ are(is) not included. A) external forces B) weight C) internal forces D) All of the above. 2. The equation of motion for a system of nparticles can be written as Σ F i = Σ m i a i = m a G , where a G indicates _______. A) summation of each particle ` s acceleration B) acceleration of the center of mass of the system C) acceleration of the largest particle D) None of the above. APPLICATIONS The motion of an object depends on the forces acting on it. Knowing the drag force, how can we determine the acceleration or velocity of the parachutist at any point in time? This has some importance when landing! A parachutist relies on the atmospheric drag resistance force of her parachute to limit her velocity. APPLICATIONS (continued) The baggage truck A tows a cart B, and a cart C. If we know the frictional force developed at the driving wheels of the truck, can we determine the acceleration of the truck? How? Can we also determine the horizontal force acting on the coupling between the truck and cart B? This is needed when designing the coupling (or understanding why it failed). APPLICATIONS (continued) A freight elevator is lifted using a motor attached to a cable and pulley system as shown. How can we determine the tension force in the cable required to lift the elevator and load at a given acceleration? This is needed to decide what size cable should be used. Is the tension force in the cable greater than the weight of the elevator and its load? NEWTON ` S LAWS OF MOTION (Section 13.1) The motion of a particle is governed by Newton ` s three laws of motion ....
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 Spring '11
 PENGSONG
 Force

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