In Motion Grade 10 Science Glenlawn Collegiate Ms W

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1 Physics of Motion Introduction: See if you can think of at least 5 words and write them around the word physics below. Leave some room and write small because we might add more Physics We encounter motion every day, but do we really know what it is or how to describe it effectively? 1 P a g e U n i t N o t e s

2 Example: Teacher Walking Around the Room Activity 1: What are some observations you can make about your teachers motion? How fast or slow something is moving we will call: What information do you think you need in order to determine an object s? What would you do with the information once you got it? What can we conclude? Remember the Scientific Method! Science is nothing more than observing the world around us, asking the right question, making an informed guess (hypothesis), doing some kind of experiment and drawing some type of conclusion. If we do this well we can discover the world around us and keep curiosity alive and well. That s Science and it s AWESOME! 2 P a g e U n i t N o t e s

3 Taking it further Observations can be both qualitative (describing words) and quantitative (measurements using numbers). Website Link: Qualitative vs. Quantitative Qualitative observations about your teacher s movement: Quantitative observations about your teacher s movement: Go back to your Activity 1 observations and circle the qualitative ones and put a rectangle around the quantitative ones. LESSON 1-Now it s time for a bunch of Vocabulary Words In order to be literate in a subject we must know the language of the subject. The following are some important concepts and terms that we need to know before moving on: Vectors and Scalars When measuring quantities in science, it is necessary to specify the direction for some quantities. Most quantities we measure are. These are measured with a or but without regard to. For example, distance travelled is a scalar as it has no direction associated with it. Temperature is also a scalar. While it can be or, it does not have a like right or left, or east or west associated with it. Ex. You leave Winnipeg and travel roughly 200km. Where are you? Some other examples of scalars are: 3 P a g e U n i t N o t e s

4 Vectors require that a be given along with the size or magnitude. They are often exactly like scalars but also have a direction associated with it. Ex. You leave Winnipeg and travel roughly 200km West. Where are you? Some other examples of vectors are: I still don t get this Website Link: Vectors and Scalars Position In order to move, you must change your position. In order to communicate our information to other persons, everyone must agree on a reference point, called the, from which we begin to take measurements. So Position is: We can easily describe distance by measuring from the origin with a ruler. Direction can be reported in many ways. It is common to use a coordinate line, that is, a line labelled -3, -2, -1, 0, +1, +2, +3 with the origin at 0: 4 P a g e U n i t N o t e s

5 In this case, we use the plus sign to indicate a position to the right of the origin and a minus sign to indicate a position left of the origin. In this unit, we will make describing direction very easy by restricting our motion along a single straight line. Instants and Intervals of Time There are two ways we can measure time, as an or as an. An instant of time is a reading at a particular, precise. For example, your leaving for school at exactly 8:15 a.m. represents an of time. If, on the other hand, we measure the time it took for you to walk from your home to school, this would represent an of time. Therefore, an instant of time relates to a, while an interval of time relates to the between two. Event Instant or interval A flight from Winnipeg to Toronto takes 1 hour and 51 minutes. The train arrives at 1:13 p.m. The next bus should come at 8:20 a.m. A phone conversation begins at 7 p.m. and ends twenty minutes later. How can we express an interval of time? How would that look in mathematical terms? Or by making a formula? Let s look at an example: calculate the time interval between two instants of time, let s say 15 seconds and 45 seconds. We probably already know the answer don t we? But if we had to make a formula what would it look like? Observe, question, hypothesize, experiment and conclude to come up with the right formula: 5 P a g e U n i t N o t e s

6 The Difference between Distance and Displacement Distance Distance is the measurement between two locations, measured along a path connecting them. It refers to how much ground an object has covered during its motion. Start Example: If you were to walk around this rectangle (4 meters east, 2 meters south, 4 meters west and 2 meters north) until you got back to the starting point, what would be the distance you travelled? Answer: Displacement So what does displacement mean? Is there a difference between and? Remember that in order to move an object, we must change the object s position. Any change in position is called a. Along a straight line, the displacement is found by the position minus the position. How do you think we can write this expression? displacement = or in symbolic form = where d stands for the position and (delta) means. Any change in a quantity is found by final value minus initial value. Therefore d reads change in position or simply displacement. Example: A toy car moves across a table in a straight line. A number line is marked on the table and the initial position of the car is -1 cm. If the car stops at the +3 cm mark, calculate the displacement of the car. 6 P a g e U n i t N o t e s

7 d 1 = -1 cm and d 2 = +3 d = d = d = (You can verify your results by counting the spaces on the number line) Distance vs. Displacement Let s go over the example we used previously for distance, and now consider displacement. If we walked around the entire square and stopped when we got back to our starting point, what would be our displacement??? Answer: Start So distance can be considered the total travelled and displacement is the difference between where you and where you. I still don t get this Website Link: Distance vs. Displacement Complete Exercise #1: BLM 9-10: Time Intervals and Distance Intervals 7 P a g e U n i t N o t e s

8 LESSON 2 - Speed and Velocity Speed When you are riding in a car, the speedometer reading indicates the speed of the car. indicates how fast an object is moving. A car that is not moving has a speed of zero. A car that is moving fast has a high speed. A car that is moving slowly has a small speed. Is speed a scalar or vector quantity? It clearly has a magnitude but does it have a direction attached to it? Think about the speedometer in your car. Does it tell you in which direction the car is moving? So speed is a quantity. We already know how speed is calculated don t we:. Guess what the symbol for speed is? Were you thinking the letter S? That would make sense but unfortunately it s not. The symbol for speed is actually. We ll talk about why later. If you travel from Winnipeg to Thunder Bay, a distance of 700 km in 7 hours what s your speed? Okay for the above question what are your units of measurement? Velocity Velocity is close to speed but slightly different. Watch for the subtle changes in the questions below. When I walked around the room, how much distance did I cover? How much time did it take? What was my speed? When I walked around the room where was my initial position? Where was my final position? What was my displacement (change in position)? Velocity is divided by. So my velocity in this case is 8 P a g e U n i t N o t e s

9 Now if I walked in a straight line from my desk to the wall, how much distance did I cover? How much time did it take? What was my speed? What was my initial position? Where was my final position? What was my displacement (change in position)? Velocity is divided by. So my velocity in this case is (remember to include a direction) As you can see, sometimes speed and velocity are quite different but sometimes they are the same. The difference is velocity has a. Velocity written as a formula it would look like this: Displacement is a vector quantity. So what do you think velocity is?. Notice that if there is an arrow on one side of the equation there will be an arrow on the other side of the equation Think of velocity as PLUS. The direction of the gives the direction of the. For example if you travel from Winnipeg to Fargo your displacement is 420 km [south]. The trip takes 4.00 hours. Your velocity would be found as follows: = 420 km[south] t = 4.00 h v = d = 420km[south] t 4.00 h = 9 P a g e U n i t N o t e s

10 Complete Exercise #2 I still don t get this Website link: Calculating speed and velocity Taking it further For question 8, if the jogger ran from one corner of the field to the other in 60s What would his speed be? What would his velocity be? (you will need to use Pythagorean s theorem to solve this one!). Let s Review We ve looked at several terms. Let s make a table: Quantity Symbol of the Quantity Unit Vector or Scalar? time instant time interval distance traveled displacement Speed velocity We ve also looked at several formulas: 10 P a g e U n i t N o t e s

11 LESSON 3 Graphing (AGAIN!) Graphing activation activity. What does every graph need? Write down your groups ideas in pencil. Then write down the classes ideas in pen. Activity Using the data tables below, prepare one graph with both sets of data for each by following the steps above. This graph represents data taken from an Indy 500 Car Race: Time (s) Distance (m) This graph represents data taken from a car driving down the highway: Time (s) Distance (m) Compare the two lines. What observations or conclusions can you make about the speeds of the two vehicles by looking at the graph? Taking it further: BLM 9-11 The Bug Race Complete Exercise #3 11 P a g e U n i t N o t e s

12 LESSON 4 - Interpreting Position-Time Graphs for Velocity Slope As you already know, there are two axes on a graph: the (horizontal) and (vertical). The of a line (or the steepness) indicates the rate of change of the variable on the y axis compared to the variable on the x axis. Since we know that change in is represented by the Greek symbol " " ( ) we can calculate the slope by using the following relation: Slope = Since the change for the variable on the y axis pertains to the vertical direction, we can call this the of the graph. Similarly, the change on the x axis pertains to the horizontal direction and can be called the of the graph. This means that we could also express the formula for slope as rise over run, like this: Slope = In order to calculate slope, choose any two points on the. To reduce the errors in calculation, choose two points that are relatively far apart. For example: Slope = 12 P a g e U n i t N o t e s

13 Using the Slope on a Position-Time Graph to find Velocity Position-Time (P-T) graphs can be read directly to give the position of an object at any in time. This interpretation of a P-T graph tells us where an object is at a given time. This information generates the position-time version of the story of the motion. The of a P-T graph gives us the of the object. This allows us to tell the velocity-time version of the story of the motion. Remember that slope refers to the steepness of a line. Therefore, the the line on a P-T graph, the the magnitude or size (speed) the velocity will be for that time interval or instant in time. Since velocity is a vector quantity, it is important that the direction of the velocity is always included. The graph below represents the position of a toy tractor as it moves across the floor. Calculate the slope by determining the rise and the run. The slope of this Position-Time graph tells us the tractor moved with an average velocity of. Since the slope was constant on the Position-Time graph, as shown by the straight line on the graph, the velocity was. 13 P a g e U n i t N o t e s

14 Examples of Position-Time Graphs Here are some typical examples of P-T graphs with various slopes. The graphs are used to describe the position of the van as it moves along a straight line path. In the graphics, the time interval between each image of the van is the same. The direction the front of the van faces gives the direction of motion. Straight lines on P-T graphs yield constant slopes, and constant velocities (speed and direction remain the same). 14 P a g e U n i t N o t e s

15 Complete Graphical Stories handout. 15 P a g e U n i t N o t e s

16 LESSON 5 - Acceleration Looking at Uniform Motion Up until now, most of the graphs of Position-Time have been -line graphs. The slope of a Position-Time graph gives the velocity. If the line is straight, the velocity is constant or uniform over that time interval. In these cases, since the velocity was uniform, there was no. Looking at Accelerated Motion or Non-Uniform Motion In motion, objects are speeding up or slowing down. Therefore, the velocity is not constant. Since the on a P-T graph gives the, a changing velocity will mean that the slope on the P-T graph must also change. A line with a changing slope is a. So, if the slope on a P-T graph becomes more positive (the line becomes steeper), the velocity is becoming more positive (larger speed in the positive direction). Since the acceleration is found from the slope of the Velocity-Time graph, the acceleration here will be. 16 P a g e U n i t N o t e s

17 Objects can also speed up travelling in the negative direction. If an object starts from rest (slope on P-T graph = 0m/s) and speeds up in the negative direction, the slope on the P-T graph will become more and more negative. Slope is 0 Slope is small negative Slope is large negative Again, the P-T graph will be a curve for which you calculate the velocity, using the slope of the line at that moment in time. Here the velocity becomes more negative (larger speed in the negative direction). The slope of this Velocity-Time is to the right and down. Therefore, since the slope on a Velocity-Time graph represents acceleration the acceleration is as well. Position-Time graphs that have curves lines with changing slopes - on them indicate that the is changing. If the velocity is changing then there must be an during that time interval. The Equation for Acceleration Acceleration has to do with an object speeding up or slowing down while moving in a straight-line path. Acceleration has to do with how changes with time. Acceleration is defined as the rate at which an object changes its velocity. It is a quantity, meaning that the direction in which acceleration acts is important. 17 P a g e U n i t N o t e s

18 TIME (S) VELOCITY (M/S) The chart to the left shows that the velocity of an object is changing with time. For each second, the velocity changes by 3 m/s. The of this object is 3 m/s/s. Since the acceleration is always 3 m/s/s, the acceleration is a acceleration Acceleration is calculated using the following relationship: Change in velocity Average Acceleration = Change in time In symbols, the following equation is used to calculate acceleration: For example, the average acceleration for the time interval from 1 s when the velocity is 3 m/s to 4 s when the velocity is 12 m/s would be found as follows. Time initial = 1 s Time final = 4 s velocity initial = 3 m/s velocity final = 12 m/s avg = avg = avg = 3 m/s/s Acceleration is expressed in units of over. The units of velocity and time determine the units of acceleration. Remember, acceleration is a. Always include a with your answer. Complete Exercise #5 18 P a g e U n i t N o t e s

19 LESSON 6 - The Link between Force and Motion Try moving the chair you are sitting in. Now try moving a chair that a person is sitting in. Which is harder to do? If you were to try to stop a rolling boulder or a rolling golf ball, which would be easier to do? These answers seem obvious but do you know why? Sir Isaac Newton ( ) synthesized all of these ideas about force and motion in his famous book, Principia. Newton said that the natural tendency for objects is to resist changes in their motion. Objects tend to keep moving with whatever motion they possess. Newton devised a of physics that is still accepted today. Newton s First Law is the following: This characteristic of matter to resist changes in motion is called. This is why Newton s First Law is often referred to as Newton s Law of. Velocity and distance an object travels after being thrown We know that the a passenger is thrown from a moving car is proportional in some way to the of the car before collision. Simply put, this means that the the car is travelling, the a passenger may be thrown in the case of a car collision. This is much like throwing a ball horizontally over a baseball field. The you throw the ball, the it travels before it lands. Recall the equation for velocity: If we rearrange the equation, then: So if you keep the time the same, the the object travels as the increases. 19 P a g e U n i t N o t e s

20 Newton s First Law So far you have touched on forces, forces, and Newton s First Law. You should expect that balanced forces have the same amount of force applied in opposite directions. In this way, balanced forces tend to cancel each other out, and usually result in a object. Example: The mini-van below is acted upon by balanced forces, and consequently remains at rest: Force A Force B When are unbalanced, that means there is a greater force in one direction than in another. When there are unbalanced forces acting on an object, this will cause the object to in a certain. Example: The mini-van below is acted upon by unbalanced forces, and consequently moves in a certain, predictable direction. Force A Force B When you looked at Newton s First Law, it was in the context of. Essentially, Newton s First Law states that an object at will stay at unless an unbalanced force acts upon it, causing the object to move. Likewise, an object in will remain in unless an unbalanced force acts upon the object, causing it to stop, slow down, or change direction. Newton s Second Law In Newton s Second Law, we are considering the relationship between an object s and its. The of an object is not simply the quantity of matter, as Newton himself theorized. The of an object is actually a of inertia of an object. What does this mean? The more an object has, the more it becomes to change the object s state of. For example, it is more difficult to budge a piano from rest than a piano bench. This is because the piano has more than the bench does and much more. Likewise, it is easy to change the motion of a baseball from a straight line to sideways, but it would be difficult to do so with an airplane. Again, the baseball has inertia and mass, so it will change its state of motion with more ease than the airplane. 20 P a g e U n i t N o t e s

21 Newton s Second Law takes these observations into consideration but also accounts for force. Newton s Second Law is often stated as: or Force = mass x acceleration. Force has units of. Mass has units of. Acceleration has units of. This law states that acceleration is proportional to the applied. If we apply a greater, there will be a greater (either speeding up or slowing down). The Law also implies that, to achieve a certain acceleration, the amount of applied force is somehow related to the of an object. The more massive an object becomes, the greater the necessary to change its speed - hence its acceleration. Finally, Newton s Second Law states that a is capable of changing the of motion on an object. Force is a quantity. If an unbalanced force is applied to an object, the object will accelerate in the direction of the unbalanced force. If you push with an unbalanced force on a person sitting in a chair with wheels the person and the chair will accelerate in the direction. If you exert an unbalanced force west on the same person, the person and the chair will accelerate in the westerly direction. Reminder: A force is any kind of or on an object. Simply applying a force does not mean that an object will move. You can push as hard as you can on a wall and never move it. Complete Exercise #6 21 P a g e U n i t N o t e s

22 LESSON 7 Newton s Third Law Most everyone has shot a basketball. To shoot the basketball into the basket, you must push the ball with a certain in a certain. While you are pushing the basketball during the shooting motion, you also feel the basketball pushing back on your hand. The force you exert on the basketball and the force the basketball exerts on your hand are a pair of - forces at work. Outcomes After completing this lesson, you will be able to: Describe Newton s Third Law Describe the everyday applications of Newton s Third Law Keywords Action Reaction Force Newton s Third Law Newton s Third Law is perhaps the most widely known and understood of the three, since it is the law of motion that everyone can easily relate to in daily activities. Newton s Third Law states that: Since forces always occur in pairs, either balanced forces or unbalanced forces, try to consider the opposite force acting when a more obvious force is acting in an everyday activity. Remember that unbalanced forces cause, but there will be no acceleration if the forces are. Example: You prepare to jump while on a skateboard... as you jump: Action: Your feet push down on the upper surface of the skateboard Reaction: The skateboard pushes up on your feet with an equal but opposite force (you seem to stick to the skateboard for a moment) The force that initiates the reaction can thus be named the, and the force that responds to the initial action can thus be called the. 22 P a g e U n i t N o t e s

23 Action Reaction Forces All forces arise from interactions. Common forces, like the attraction of gravity and the attraction and repulsion of electric and magnetic forces, always occur in pairs. Whenever two objects interact with each other, they exert these types of forces on each other. We call these force pairs or - forces. Newton summarized these interactions in his third law: For every action, there is an equal and opposite reaction. What make the sprinkler head turn? To make the water fly away from the nozzle of the sprinkler, a force must be exerted on the water by the sprinkler nozzle. This is the. By Newton s Third Law, there must be an equal but opposite. This reaction force is the force of the water on the sprinkler nozzle. This force pushes the nozzle in the opposite direction, causing the nozzle arms to spin. Two students of different masses pull on two pieces of rope that are connected by a spring scale to measure force. What does the scale read? How do we know that the force exerted by the small student is exactly the same as the force exerted by the heavier student? In all cases, the of the forces are and the forces act in opposite directions. 23 P a g e U n i t N o t e s

24 Summary Newton s Third Law states that for every action there is an equal and opposite reaction. The force that initiates the reaction can thus be named the, and the force that responds to the initial action can thus be called the. Action-reaction pairs of forces are not. The action force acts on object 1 but the reaction force acts on object 2. Complete Exercise #7 LESSON 8 Momentum and Impulse Have you ever noticed that while tobogganing down a steep slope, you have a hard time stopping? This is because of your. You might have heard the word momentum before and may have an idea what it means. In this lesson, you will study the concept of momentum and things that increase and decrease momentum. Outcomes After completing this lesson, you will be able to: Define Define Relate impulse to in momentum for everyday situations Discuss the importance of in a golf swing or kicking a soccer ball Keywords Momentum Mass Velocity Impulse Force acting over time 24 P a g e U n i t N o t e s

25 Momentum In everyday life, we often use the word to describe a sports team or a political party that is on a roll and is going to be difficult to stop. The common usage of the term momentum has roots in the physics world. Any object that is moving has momentum, and in order to bring the object to rest we must change this momentum to zero. What makes an object difficult to bring to rest? Would you rather collide with a train moving at 2 m/s or a mosquito moving at the same speed? The answer is obvious: the train can crush a car. However, in the second case, the pesky mosquito never even dents your windshield. Momentum is a term we use in physics to describe a quantity of. If an object is in motion then it has momentum. What are the characteristics of momentum? Well, from our train and mosquito example, we know that the mass of the train makes it more difficult to stop than a mosquito moving at the same speed. This should make sense if you recall from our discussion of Newton s laws that mass is a resistance to. Certainly, more mass means more resistance to acceleration, and the more difficult it is to bring the object to rest. However, momentum is not the same as mass. A massive boulder resting on the side of the road has no momentum at all it is already at rest! Objects that are moving fast are also hard to. Bullets have a very small mass but it can be extremely difficult to try and stop one! If we wish to bring an object in motion to rest, we must take into account its as well as its. Newton called this the of. Simply stated, if a moving object has more mass, it has more momentum, and if an object has more velocity, it has more momentum. That is, if either the mass or velocity (or both) of an object, the object will be more difficult to bring to rest. Impulse and Momentum In order to change motion we need to apply an unbalanced force. If we continue to apply a force for a long period of time, the object will continue to, increasing (or decreasing) its velocity more and more. 25 P a g e U n i t N o t e s

26 We call the amount of force and the time during which the force is applied the. If we have more force, we have more impulse. Additionally, if we apply the force for a longer period of time, we also have more impulse. In this way, impulse is proportional to and. Consequently, we can define impulse as the product of force and time. The fact that impulse depends on both force and time means that there is more than one way to apply a large impulse to an object you can apply a very large force for some time, or apply a smaller force for a very long time (or both!). If an unbalanced force acts on an object it will always cause the object to. The object either speeds up or slows down. If the force acts opposite to the object s motion, the object slows down. If a force acts in the same direction as the object s motion, then the object speeds up. Thus, when the velocity of the object is changed, the momentum of the object is also changed. When something exerts a force on you, it also exerts an impulse on you. Forces and impulses always go together. Very simply stated, impulse changes. This relationship is very closely related to Newton s Second Law. Using the Impulse-Momentum Relationship If you play sports, your coach has been teaching you about and for many years. In most sports you wish to change the of an object for many different purposes. Hitting a home run, bumping on the volleyball court, deflecting a shot on goal, driving a golf ball, or serving on the tennis court require that you change the (and therefore the ) of the ball or puck by applying an impulse. In order to improve your performance, the coach might first suggest that you hit the ball by building up strength. Increasing your fitness enables you to apply a larger. In this case, a larger force acting for the same time gives a larger. Later, your coach will constantly remind you about in your technique. By developing sound technique, as you follow through, you can increase the amount of the force acts on the object. In this case the same force acting for a larger gives a larger. Sometimes we want small forces applied on objects, and other times we want large forces. However, if you try to apply too much force you can lose control and your timing is less accurate. 26 P a g e U n i t N o t e s

27 Here are some everyday examples of impulse and momentum in operation: You are sliding down a hill on your toboggan with great speed but need to stop before hitting a boulder. In order to your momentum, you could dig your heels into the snow (applying a force) for a minute or two (time) to slow the toboggan down to a safe speed. You are riding your bike to the swimming pool and will be late for your lesson if you don t hurry up. In order to your momentum, you need to pedal harder (more force) for the next five blocks (a longer period of time). Summary Momentum is a of. Objects that are have momentum. Objects that are at rest have no momentum. Moving objects with masses have momentum than moving objects of smaller mass moving at the same velocity. Momentum depends both on the and of an object. Complete Exercise #8 27 P a g e U n i t N o t e s

28 LESSON 9 Conservation of Energy It is likely that you have seen the scene of a car collision and have observed the remains of the destruction. You may have noticed that parts of the car are crumpled or torn off, that glass is broken, and that fluids may be leaking from the engine. You might also smell some odours that you have never experienced before, and you may also see and smell smoke. Of course, if you witnessed the actual collision, you would have heard the sounds of the two cars colliding and possibly hitting other objects as well. All of these observations are examples of the Law of Conservation of Energy at work. The states that energy cannot be or, but can only be or into different forms of. In a car crash, in addition to converting from one form to another, energy is also transferred from the car to the, through the body of the car, and through the in the car. For example, energy from the movement of the car can be transferred to the, which will, or through the of a passenger, which may. In a car collision, huge amounts of kinetic are converted and transferred to other systems. Energy can be converted to several different types of energy, such as; 1. Kinetic energy: the energy of motion 2. Potential energy: the energy of position with respect to the surface of the Earth (e.g., an object falling from two stories up will not reach as great a final velocity and kinetic energy as an object that falls from 16 floors up) 3. Heat energy: the energy of molecules in motion 4. Sound energy: the disturbance of molecules As the initial kinetic energy reduces to, other forms of energy. For example, less motion could mean more and. After a crash has taken place, the of the car is reduced to, which means there is no more kinetic energy. All this kinetic energy has been transferred and to other and systems. This is for passengers, as they also are objects moving along with the car with great amounts of kinetic energy. When the second collision occurs, forces this kinetic energy out of the passengers. The application of the forces can result in injury. 28 P a g e U n i t N o t e s