Physics Notes - Vectors , Circular Motion, Newton's 1st and 2nd Laws
Physics Notes - Vectors , Circular Motion, Newton's 1st and 2nd Laws CLA PHY 14.003PRISM
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This 5 page Class Notes was uploaded by Clairissa Cole on Wednesday February 3, 2016. The Class Notes belongs to CLA PHY 14.003PRISM at Mercer University taught by Dr. Chamaree de Silva in Winter 2016. Since its upload, it has received 83 views.
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Date Created: 02/03/16
Physics Ch. 3 - Intro to Vectors Monday, January 18, 2016 7:09 PM • Scalars vs. Vectors Scalars : a number w/ units ex: speed, time, distance Vectors:a value with both magnitude & direction ex: displacement , velocity,acceleration • Componentsof a vector -> R Y ⁰ X Example Problem : Find the x and y componentsof a position vector r-> of magnitude r = 75m, if its angle relative to the x- axis (a) 35.0 degrees (b) 65.0 degrees. Manipulating Vectors Friday, January 22, 20165:00 PM Multiplying Vectors by a Scalar -Suppose Vector A has a magnitude of 2 so, 3A has a magnitude of 6 2A 3A Unit Vector -has a magnitude of exactly 1 *think unit circle* -can point in any direction 1 Given a unit vector u, it's arrowhead must lie on the unit circle -Vector Notations : ˰ x-component: ˰ y- component: ˰ ˰ Ex. Vector b = -16m Vector Addition -You can add vectors in two ways : Graphically or Algebraically A + B = C [Vector C is the resultant vector ] -When adding vectorsgraphically, you align them tip-to-tail Ex. Vector A is 5.5cm points along positivex-axis. Vector B is 7.5cm and points 150⁰ from positive x-axis in the counter clockwise direction. -How to solve? 1. Solve for x & y componentsof each vector 2. Add x components, add y components 3. Draw resultant vector componentsthen solve for hypotenuse and angle. Newton's Laws of Motion Monday, February 1, 2016 7:22 PM ▪ Forces - push or pull on an object - Ex: if you have a book resting on a table Normal Force (upward by table) friction (weight (w=mg)) -Force is a vector: it has magnitude and direction (push or pull) • Net Forces - vector sum of all the individual forces. -Ex: Net Force = F 1 + F2 1st Law : *If an object is at rest, it will stay at rest as long as there is no net force acting on it. *An object moving at constant velocity, continues to move with the same speed in the same direction as long as there is no net force acting on it. => Also known as the Law of Inertia : Object won't change motion unless forced to do so. Object at rest, stays at rest Object already moving with constant velocity won't change speed or direction. • 2nd Law : * *If you have an unbalanced force(netforce does not = 0) ; you have acceleration (not constant velocity) ○ Force is measured in Newtons (N) => Ex: Suppose your mass is 81 kg. Find your weight on the Earth and on the Moon. Circular Motion Monday, February 1, 2016 5:02 PM The velocity vector is tangential to the circular path. magnitude(speed) -assume constant speed vectors are the same length. Velocity Vector has : direction (changes with time) Since acceleration is -we can represent this graphically by using vector subtraction(addition) always points to the center ; it is centripetal acceleration ( center - seeking in Latin) An object moving in a circular motion has: - Constant Speed - Changing velocity (because the direction is always changing) - Acceleration (inwards toward center of the curve) *allows object to change direction* A particle is in uniform circular motion if it travels around a circular path at a constant speed. magnitude Acceleration has : direction : always toward canter How to calculate how long it would take for an object to travel one period of revolution ?