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## Chapter 10

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**Chapter 10**Motion & Momentum**Ch 10.1 – What is Motion?**• All matter is constantly in motion • Motion involves change in position 1. An object changes position relative to a reference point**2. Distance – the total length of the route an object**travels when it moves**3. Displacement – includes the distance and direction of**the stopping point from the starting point**C. Speed – distance traveled divided by the time taken to**travel that distance 1. Formula for speed: speed = distance/time 2. SI Unit for speed: meters per second (m/s)**Calculating Speed**• Calculate the speed of a swimmer who swims 100m in 56s • Speed = distance / time or • D = 100m • T = 56s • Speed = 100m = 1.8 m/s 56s**3. An object in motion can change speeds many times as it**moves from one point to another, speeding up or slowing down a) Average speed – the total distance traveled divided by total time taken**b) Instantaneous speed – an object’s speed at a**particular moment in time c) Constant speed – occurs when an object travels at a steady rate with the same instantaneous speed for some period of time**D. Graphing Motion**1. Motion can be graphed on a distance-time graph a) Distance is plotted on the vertical axis b) Time is plotted on the horizontal axis**3. A horizontal line indicates that no change in position is**occurring and the speed is zero**E. Velocity – the speed of an object AND its direction of**motion 1. Velocity changes if either or both of these factors is altered**Ch 10.2 - Acceleration**• Acceleration – change in velocity divided by the time for the change to occur 1. Can include an object speeding up, slowing down, and/or changing direction**B. Acceleration can be calculated if you know how an**object’s velocity has changed during a given time period 1. Formula for acceleration: Acceleration = final speed – initial speed time a = (Sf – Si) / t**a) SI Unit for acceleration:**meters per second squared (m/s2) b) Acceleration number will be positive when an object is speeding up and negative when slowing down**Calculating Acceleration**• Calculate the acceleration of a bus whose speed changes from 6m/s to 12m/s over a period of 3s • A = (final speed – initial speed) time • A = 12 m/s – 6 m/s = 6 m/s = 2 m = 2 m/s2 3 s 3 s s x s**C. Graphing Acceleration**1. Acceleration can be graphed with a speed – time graph a) Speed is plotted on the vertical axis b) Time is plotted on the horizontal axis**2. An object that is speeding up will have a line that**slopes upward 3. An object that is slowing down will have a line that slopes downward 4. An object moving at a constant speed will have an acceleration of zero, and a horizontal line on the graph**Speed – Time Graph AKA…**(speed) (constant speed) Positive Acceleration Negative Acceleration**Ch 10.3 - Momentum**• The amount of matter that an object has is its mass 1. Inertia – the tendency of an object to resist change in motion; directly correlates to its mass**B. Momentum – measure of how hard it is to stop an object**1. Calculated as mass times velocity 2. Formula for momentum: momentum = mass x velocity (p = mv)**Calculating Momentum**• Calculate the momentum of a 14-kg bicycle traveling north at 2 m/s • P = mv • P = 14 kg x 2 m/s north • P = 28 kg x m/s north**3. Momentum increases if the mass or velocity of the object**increases**4. Momentum has direction that is the same direction as its**velocity ex: P = 28 kg x m/s north**C. Law of Conservation of Momentum**1. The total momentum of objects that collide with each other does not change**2. There are many ways collisions can occur**a) Objects may stick together and move still stuck together b) Objects may bounce off each other and transfer momentum from one to the other**3. In all cases, the total momentum of the objects that**collide is the same before and after the collision