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 More practice problems p.284

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

2. The steeper the line the faster the speed

http://www. broadeducation http://www.broadeducation.com/htmlDemos/AbsorbPhysicsAdvd/DistanceTime/page.htm

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 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

1. Formula for acceleration: 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 More practice problems p.290

C. Graphing Acceleration 1 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 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 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

Which has more Momentum?

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 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