St. Augustine Preparatory School August 11, 2015 Lecture Physics Chapter 2 St. Augustine Preparatory School August 11, 2015 Lecture

Information about the quiz (tomorrow’s class) Your quiz is going to be 10 questions long and all short answer The questions will be on the whiteboard through the projector, so please bring a piece of paper to write on No devices are to be used in place of a calculator, besides a calculator Topics we covered: scientific method, precision/accuracy, unit conversions, significant figures, determining units of an answer, using units to solve problems without knowing a formula (if someone eats 3 cheeseburgers an hour for 2 hours, how many cheeseburgers have they eaten?)

Some review 12m + 13.6m + 14.22m = ______ (correct sig. fig. and unit required) 1.456m / 2.32 s = _______ (correct sig fig and unit required) 2.3x102m x 1.532m = _________ (correct sig fig and unit required) What is the difference between precision and accuracy? Can you be precise without being accurate? If you drive 49.0km/h for 97.0 minutes, what distance will you travel? Convert 1 172m to km Convert 1.2g to mg Convert 1 328 256ml to kL

The beginning of Chapter 2: Motion in 1 Dimension The world around us is 3 dimensional (x, y, and z) This means that all objects have a length, width, and height We are going to begin by looking at 1 dimensional motion An example of this would be a train moving on a straight track. Objects can move forward or backward; not left or right, or up and down.

Frames of Reference We use frames of reference to measure changes in position. If you don’t know where something started, it is difficult to measure how far it has travelled Frames of reference must remain fixed (they do not move When a bus departs a bus stop, that bus stop can be used as a frame of reference

Distance and Displacement Although the two terms sound similar, they are very different Distance refers to how much ground an object has covered Distance traveled can be measured with an odometer in a car Displacement refers to the distance between the end point and the starting point, if a straight line is drawn between the two Ie. How far is the object from where it originally began

Displacement Displacement can be either positive or negative Negative displacements represent movements to the left or backwards Throughout physics, positive numbers will represent movements to the right (east) or upwards (north). Negative numbers will represent movements to the left (west) or downward (south)

Example Problems Ex 1. Susan walks 11m forward, turns around and walks 6 meters in the opposite direction, and finally walks another 3 meters forward. What distance has Susan walked? What is Susan’s displacement? Ex 2. Mark rides his motorcycle down his street 132m to the right, before realizing he was travelling in the wrong direction. He turns around and rides 162m in the opposite direction and ends up at his friends house. What distance did Mark travel and what is his displacement?

Vavg= ∆𝑥 ∆𝑡 = (xf-xi) / ( tf - ti) Average Velocity Average Velocity is defined as the displacement divided by the time interval that the displacement took place over Vavg= ∆𝑥 ∆𝑡 = (xf-xi) / ( tf - ti) Example: Steven rides his motorcycle 32m to the right in 4.8 seconds. What is Steven’s average velocity?