Week 2 of Physics Notes
Week 2 of Physics Notes PY 205
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This 3 page Class Notes was uploaded by Iman Usmani on Tuesday January 12, 2016. The Class Notes belongs to PY 205 at North Carolina State University taught by Professor Dougherty in Winter 2016. Since its upload, it has received 14 views. For similar materials see Physics for Engineers and Scientists in Engineering and Tech at North Carolina State University.
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Date Created: 01/12/16
PY 205 Daniel Dougherty Week 2 Notes Chapter 3 - Kinematics in two or three dimensions Vectors and scalars – velocity is how fast and in what direction the particle is moving o Magnitude – vector quantity o Scalar quantities are specified by numbers and units Addition of vectors – graphical methods o above D = displacement vectors o above v = velocity vectors Resultant displacement – represented by the arrow above the Dr o This should be smaller than the sum of the first displacement of the vector and the second displacement of the vector o The sum of the two vectors is called the resultant o Create a triangle by connecting the head and the tail of the two vectors Three methods to find the two dimensional vectors o Addition Connect the head and the tail by a line to create a triangle to measure the displacement between the two vectors o Subtraction When you want to change the direction and move the second vector up so that the head and the tail are touching. V1 – V2 = V1 + (-V2) Create a line o Scale of multiplication Important to use if you want to change a vector to be negative (multiply by a factor of -1) Makes the same magnitude but changes the direction V1 3V1 Chapter 4 Dynamics – connection between force and motion o Force = push or pull of an object o Contact forces – force is exerted when an object comes into contact with another o Objects fall because the forces of gravity o To find the force of gravity on an object, you can use the spring scale to measure the “weight” of the object o Force has direction and mass Newton’s first law of motion o Every object continues in its state of rest or uniform velocity in a straight line, as long as no net force acts on it Inertia - tendency of an object to maintain in its state of rest of uniform velocity in a straight line Inertial reference frames – where the first law holds true Where the inertial law does not hold true is called the noninertial reference frames Mass – quantity of matter – the measure of inertia on an object o More mass = greater force needed to give it a particular acceleration Newton’s second law of motion – the acceleration of an object is directly proportional to the net force acting on it. And it inversely proportional to the object’s mass o The direction of the acceleration is in the direction of the net force acting on the object o Force – an action capable of accelerating an object o Force is a vector o Direction if only affected by the net force of the direction The unit is called a Newton (N) Dyne = the unit of force needed to impact an acceleration – 1 dyne = 10^-5 N Newton’s third law of motion – whenever an object exerts force on a second object, the second object exerts and equal force in the opposite direction of the force o “Every action has an equal and opposite reaction” o Action and reaction are acting on different objects Remember: what object given force is exerted and by what force is it exerted? The force of gravity and the normal force o Gravitational force on an object o mg = is called the object’s weight o Contact force – when the two objects are in contact with one another When contact force acts perpendicular to the common surface – it is called the normal force Solving problems with Newton’s laws – free-body diagrams o Acceleration of an object is proportional to the net force acting on the object Net force – vector sum of all forces acting on the object o Free-body or force diagrams – how to draw: 1. Choose on object 2. Draw an arrow to represent each force acting on it 1. Has no net force working on it, objects are moving at a constant velocity, does not have a changing speed 2. Moves with a changing speed 3. Has the largest magnitude of force and the objects move with a changing speed 4. The objects move with a changing speed
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