PHY 102 1nd Edition Lecture 8 Outline of Last Lecture I. MotionII. Uniformly Accelerated Motion (UAM)III. Blue Book 3.1Outline of Current Lecture I. KinematicsCurrent LectureI. Kinematicsa. Motion of an object is always described in relation to an observer. The object and the observer are considered as pointsb. Studies the three fundamental qualities:i. Position vectorii. Velocity vectoriii. Acceleration vectorc. Vector = arrowd. Position vector = an arrow with its tail at the observer and its tip at the (moving) objecti. If the position vector changes, we say the object is moving relative to the observerii. Observer is not moving1. Driving down the highway, you can consider yourself the observer which means you aren’t moving, but the highway isiii. It is wrong to say that the car is moving, but the tree is not! (You are not saying who the observer is --> has to be relative)1. You can say the car moves relative to the tree or the tree moves relative to the cariv. All objects that don’t move relative to one another are said to belong to the same reference frame (RF)These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.1. The hardest thing to get used to is the fact that earth is not our only RFv. Motion of an object relative to an observere. Displacement = the change in the position vectori. Final position vector – initial position vectorii. It is the arrow that connects the initial position to the final position, the latter changing with time∆r--> = rf - riDisplacement is always a straight arrowDistance is the length of the path traveled (curvy line)iii. The same as long as the observers are in the same RFf. Average velocityi. What you get when you divide displacement vector by timev-->avg= ∆r-->/∆t1. When the time becomes infinitesimally short, you get instantaneous velocityg. Average speedi. When you divide the length of the path by time, you get the average speedvavg = distance/∆t1. When the time becomes infinitesimally short, you get instantaneous speedh. For a car, the magnitude of the instantaneous velocity is what you read on the speedometer, and its direction is the direction of the car’s
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