Motion Part 1: Constant Speed What is Physics? Physics is the study of the physical world (energy and matter) and how they are related. Ms. Levine 1
Create your own motion map What is the purpose of these motion maps? Connor runs quickly at a constant speed to the east. Madelyn runs slowly with a constant speed to the west. Draw a motion map for each below. (use the lines to help you) Connor What is it showing us? Madelyn What do you think about when you hear the word motion? Ms. Levine 2
In this unit, we will be discussing movement in a straight line. What do we need to know to describe motion? direction (left-right, forward-backward, north-south) units of measure a starting point (what happens if the starting point were to change? What do we need to know to describe motion? Frame of Reference What is speed? - the place from which motion is observed and measured Let's watch a couple short videos to help us better understand this concept. Frame of Reference Video!.mp4 Frame of Reference #1.mp4 the distance traveled divided by the time it took to travel that distance so to calculate speed we need distance and time How far is a second?.mp4 distance - SI Units Speed and Distance doesn't require us to define where we started from and where we ended up. time - speed - it just measures how far we traveled and how long it took to travel that far Much of Physics is about knowing where something is and how its position changes with time Ms. Levine 3
Displacement What is displacement? For instance, if you drive 60 miles from Pennsylvania to New Jersey +y Displacement - the change in position ( x) and then traveled 20 miles back towards Pennsylvania, -x Pennsylvania +x New Jersey - how far you are from where you started How many miles did you travel? How far are you from where you started? In what direction? -y Δx = X f - X o Distance can only be a positive value since it is impossible to travel a negative distance. Displacement However, displacement can be positive or negative since you can end up to the right or left of where you started. +y +y Vectors and Scalars Scalar - a quantity that has only a magnitude (number or value) Vector - a quantity that has both a magnitude and a direction Which of the following are vectors? Scalars? -x x o x f +x -x x f x o +x Quantity Vector Scalar Time Distance -y -y Displacement Speed Displacement is positive. Displacement is negative. 1 How far your ending point is from your starting point is known as: 2 A car travels 60m to the right and then 30m to the left. What distance has the car traveled? A distance B C displacement a positive integer - x +x D a negative integer Ms. Levine 4
3 You travel 60m to the right and then 30m to the left. What is the magnitude (and direction) of our diplacement? 4 Starting from the origin, a car travels 4km east and then 7 km west. What is the total distance traveled? - x +x A B 3 km -3 km C 7 km D 11 km 5 Starting from the origin, a car travels 4km east and then 7 km west. What is the net displacement from the original point? 6 You run around a 400m track. At the end of your run, what is the distance that you traveled? A 3 km west B 3 km east C 7 km west D 11 km east 7 You run around a 400m track. At the end of your run, what is your displacement? Average Velocity Speed is defined as the ratio of distance and time distance traveled Average speed = s = d time elapsed t Speeds are always positive, since speed is the ratio of distance and time; both of which are always positive. Velocity is defined as the ratio of displacement and time Average velocity = displacement time elapsed Δx v = Δt But velocity can be positive or negative, since velocity is the ratio of displacement and time; and displacement can be negative or positive. Ms. Levine 5
8 Which of the following is a vector quantity? A time B velocity C distance D speed 9 Average velocity is defined as change in over a period of. A B C D distance, time distance, space displacement, time displacement, space 10 You travel 60 meters to the right in 20 s; what is your average velocity? 11 An elephant travels 60 meters to the left in 20 s; what is the average velocity? 12 You travel 60 meters to the left in 20 s and then you travel 60 meters to the right in 30 s; what is your average velocity? 13 You travel 60 meters to the left in 20 s and then you travel 60 meters to the right in 30 s; what is your average speed? Ms. Levine 6
14 You run completely around a 400 m track in 80s. What was your average speed? 15 You run completely around a 400 m track in 80s. What was your average velocity? 16 You travel 160 meters in 60 s; what is your average velocity? Let us transpose our motion maps to a position vs time graph. Ms. Levine 7
Now in reverse, a position vs time graph to a motion map. Ms. Levine 8
What does a position vs time graph look like of an object that is not moving? Moving at a constant velocity? Draw below. motionless constant velocity Ms. Levine 9