Lesson 3.1 Motion Descriptors PDF

Lesson 3.1 Motion Descriptors General Physics 11/2 Science, Technology, Engineering, and Mathematics Motorcycles and tricycles are two of the main modes of transportation in the Philippines. 2 One of the advantages that might convince someone to...

Lesson 3.1 Motion Descriptors General Physics 11/2 Science, Technology, Engineering, and Mathematics Motorcycles and tricycles are two of the main modes of transportation in the Philippines. 2 One of the advantages that might convince someone to buy a motorcycle is that it can pass through small spaces during heavy traffic congestion in the cities. 3  With this in mind, can we actually say that motorcycles are faster than normal vehicles? In order for us to answer this more scientifically, we have to understand first what motion descriptors are. 4 What are motion descriptors? 5  Learning Competencies This lesson serves as a prerequisite for the following DepEd competencies: Convert a verbal description of a physical situation involving uniform acceleration in one dimension into a mathematical description (STEM_GP12Kin-Ib-12). 6  Learning Competencies This lesson serves as a prerequisite for the following DepEd competencies: Recognize whether or not a physical situation involves constant velocity or constant acceleration (STEM_GP12Kin-Ib-13). 7  Learning Objectives At the end of the lesson, you should be able to do the following: Define motion. Enumerate the different motion descriptors. Describe velocity and acceleration. Explain the relative nature of motion. 8 How can we say that an object is moving? 9 Motion Consider a soccer ball kicked by a soccer player. 10 Motion The ball ‘moves’ because the soccer player kicked it. 11  Motion The ball changed position from the soccer player’s initial position to a target position, preferably the goal. 12  Motion Motion is defined as the change of position of an object in a specific span of time relative to an observer. 13  Motion Motion requires position and time. how much time, t ball’s initial position ball’s final position x0 xf 14 What are the quantities that describe motion? 15  Motion Descriptors Time It is a quantity that describes when an event took place. It is a necessary parameter to describe and to observe changes in a specific space. It is measured in terms of seconds (s) and usually noted by t. 16  Motion Descriptors Distance and Displacement 17  Motion Descriptors Distance and Displacement Distance is always greater than or equal to displacement. These two quantities can only be equal if the object in motion travels towards one direction only and does not go back to its original position. 18  Motion Descriptors The skater moves from A to B, B to C, and finally, C to D. 19 Motion Descriptors What is the distance covered by the skater? 20  Motion Descriptors In general, distance can be calculated using the equation below. Distance is the total length travelled by an object. 21 Motion Descriptors What is the displacement covered by the skater? 22  Motion Descriptors In general, displacement can be calculated using the equation below. Displacement is defined as the length of the line that separates the initial position (x0) to the final position (xf). 23  Motion Descriptors Speed and Velocity These are quantities that combine the concept of time and space. Speed is the rate of change in position. It can be noted as v or s and has a unit of m/s or ms-1. Velocity is the rate of change in position with respect to a reference point. The direction on how the object moves is important in determining velocity. 24  Motion Descriptors Speed and Velocity 25  Motion Descriptors Speed and Velocity Mathematically, speed and velocity can be described using the equations below. speed velocity (average) 26 Motion Descriptors What is the skater’s speed? 27 Motion Descriptors What is the skater’s velocity? 28 At which instance are speed and velocity equal? 29  Motion Descriptors Acceleration It describes how an object changes its velocity per elapsed time. It is a vector quantity with an SI unit of m/s2. 30  Motion Descriptors Acceleration Three ways to say that an object is accelerating: 1. if the magnitude of the velocity of the object is changing; 2. if the direction of the motion of the object is changing; and 3. if both the magnitude of the velocity and the direction of motion are changing. 31 What are the indications of the sign of acceleration? 32  Motion Descriptors Signs of Acceleration Positive acceleration ⟶ a and v are of the same direction ⟶ speeding up Negative acceleration (deceleration) ⟶ a and v have opposite directions ⟶ slowing down Zero acceleration ⟶ object is travelling at constant v or not moving at all 33  Relative Nature of Motion Motion is relative. This means that an object which is moving for you might not be moving relative to another person. Consider you and your classmate who is sitting on your respective chairs. Are you in motion? 34 Relative Nature of Motion Can you tell what does each person see in this figure? 35  Check Your Understanding Write T if the statement is true and F if not. 1. Motion is relative. 2. If you are on a train and you look at a tree outside the train, that tree is moving relating to you. 3. People sitting on a bus are not moving relative to each other but are moving relative to the ground. 36  Check Your Understanding Identify the correct motion descriptor described in each item. 1. It is measured in terms of seconds. 2. It is defined as the rate of change in velocity. 3. If this quantity is negative, it means that the object is slowing down. 37  Let’s Sum It Up! Motion is defined as the change of position of an object in a specific span of time relative to an observer. There are six motion descriptors, namely: time, distance, displacement, speed, velocity, and acceleration. 38 Let’s Sum It Up! ○ Time is a quantity that describes when an event took place. ○ Distance is the total length traveled by a moving object. It is a scalar quantity. ○ Displacement is the length and direction of the line that connects the initial and final position. It is a vector quantity. 39 Let’s Sum It Up! ○ Speed is the rate of change in position. It is a scalar quantity. ○ Velocity is the rate of change in position with respect to a reference point. It is a vector quantity. ○ Acceleration is the rate of change in velocity. It is a vector quantity 40  Let’s Sum It Up! A positive acceleration means that the object is speeding up, and a negative acceleration means the object is slowing down. If the acceleration is zero, then the object is following a constant motion. 41  Key Formulas Concept Formula Description Use this formula to Distance solve for distance if where the positions are given. d is distance x is position 42  Key Formulas Concept Formula Description Use this formula to Displacement solve for displacement where if the initial and final positions are given. is displacement xf is the final position xi is the initial position 43  Key Formulas Concept Formula Description Use this formula to Speed solve for speed if the where distance and the time v is speed elapsed are given. d is distance t is elapsed time 44  Key Formulas Concept Formula Description Use this formula to Velocity solve for velocity if the where displacement and the time elapsed are given. is velocity is displacement t is elapsed time 45  Key Formulas Concept Formula Description Acceleration Use this formula to where solve for acceleration if the object’s initial and is acceleration final velocity, and the is final velocity time elapsed are given. is elapsed time 46 Challenge Yourself A car that is traveling at a constant speed passed through a curved road. Do you think the car accelerated? Why or why not? 47 Bibliography Faughn, Jerry S., and Raymond A. Serway. Serway’s College Physics (7th ed). Singapore: Brooks/Cole, 2006. Hewitt, Paul G. Conceptual Physics (11th ed). New York: Pearson Education. 2010. Homer, David, and Michael Bowen-Jones. Physics Oxford IB Diploma Programme. UK: Oxford University Press, 2014. Sang, David, Graham Jones, Gurinder Chadha, and Richard Woodside. Cambridge International AS and A Level Physics Coursebook. UK: University Printing House. 2014. Serway, Raymond A., and John W. Jewett, Jr. Physics for Scientists and Engineers with Modern Physics (9th ed). USA: Brooks/Cole, 2014. Young, Hugh D., Roger A. Freedman, and A. Lewis Ford. Sears and Zemansky’s University Physics with Modern Physics (14th ed). USA: Pearson Education, 2012. 48