Speed Physics

9 Key excerpts on "Speed Physics"

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  An Introduction to Physical Science

  • James Shipman, Jerry Wilson, Charles Higgins, Bo Lou, James Shipman(Authors)
  • 2020(Publication Date)
  • Cengage Learning EMEA

    (Publisher)

  28 CHAPTER 2 Did You Know? Section Speed and velocity are different physical quantities. 2.2 A race car going around a circular track at a constant speed is accelerating. 2.4 A football quarterback cannot throw a “straight-line” pass. 2.5 Motion Give me matter and motion, and I will con- struct the universe. ● René Descartes (1596–1650) Robert Harding World Imagery/Robert Harding/Alamy Stock Photo H aving been introduced to measurement and units, you are ready to begin your study of physics. Physics, the most fundamental physical sci- ence, is concerned with the basic principles and concepts that describe the workings of the universe. It deals with matter, motion, force, and energy. There are various areas of physics: ● ● Classical mechanics is the study of the motion of objects moving at relatively low speeds. ● ● Waves and sound is the study of wave motion and its application to sound. ● ● Thermodynamics is the study of temperature, heat, and thermal processes. ● ● Electromagnetism is the study of electricity and magnetism. ● ● Optics is the study of the properties of light, mirrors, and lenses. ● ● Quantum mechanics is the study of the behavior of particles on the microscopic and submicroscopic levels. ● ● Atomic and nuclear physics is the study of the properties of atoms and nuclei. ● ● Relativity is the study of objects traveling at speeds approaching the speed of light. We will delve into all of these areas, except relativity, and begin with classical mechanics and the study of motion.

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  Inquiry into Physics

  • Vern Ostdiek, Donald Bord(Authors)
  • 2017(Publication Date)
  • Cengage Learning EMEA

    (Publisher)

  Velocity is an example of a physical quantity called a vector. Vectors have both a numerical size (magnitude) and a direction associated with them. Quantities that do not have a direction are called scalars. Speed by itself is a scalar. Only when the direction of motion is included do we have the vector velocity. Similarly, we can define the vector displacement as Table 1.2 Some Speeds of Interest Description Metric English Speed of light, c (in vacuum) c c 3 3 10 8 m/s 186,000 miles/second Speed of sound (in air, room temperature) 344 m/s 771 mph Highest instantaneous speeds: Running (cheetah) 28 m/s 75 mph Swimming (sailfish) 30.6 m/s 68 mph Flying—level (merganser) 36 m/s 80 mph Flying—dive (peregrine falcon) 108 m/s 242 mph Humans (approximate): Swimming 2.5 m/s 5.6 mph Running 12 m/s 27 mph Ice skating 14 m/s 31 mph Figure 1.9 Hand-held GPS receiver capable of measuring speed and direction of motion, that is, velocity. Ovu0ng/Shutterstock.com Velocity Speed in a particular direction (same units as speed). Directed motion. DEFINITION Copyright 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. WCN 02-300 22 Chapter 1 The Study of Motion distance in a specific direction. For the airplane referred to earlier, the distance it travels in 2 hours is 200 miles. Its ac e e - tual location can be determined only from its displacement— t t 200 miles due north, for example. The basic equation for speed, v 5 Dd/ Dt, is also the equation for velocity (that’s why v is used) v v with d representing a vector displacement. We can classify most physical quantities as scalars or vectors. Time, mass, and volume are all scalars because there is no direc- tion associated with them. Vectors are represented by arrows in drawings, the length of the arrow being proportional to the size or magnitude of the vector (Figure 1.10).

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  Engineering Science N2 Student's Book

  TVET FIRST

  • MJJ van Rensburg(Author)
  • 2016(Publication Date)
  • Troupant

    (Publisher)

  Speed = distance covered time taken v = Δ s Δ t Note In physics we use the upper case Greek letter delta ( Δ ) to denote a change in any variable quantity. The lower case Greek letter delta ( δ ) is used to denote an infinitesimal (very small) change or an incremental change. Speed is an instantaneous measure because it is measuring the speed at a specific point in time. Average speed is a measure of the average of all the instantaneous speeds across a journey. Speed is measured in m/s (also written as m.s –1 ) or km/h. If a car covers a distance of 80 km in 1 h, the average speed is 80 km/h. Because distance is a scalar quantity, speed is also a scalar quantity because it has magnitude but no fixed direction. instantaneous: occurring at a specific point in time 7 Velocity Velocity ( v ) is the speed of an object in a specific direction. Velocity is therefore the rate of change of the displacement. It is the displacement undergone per time unit. Velocity = displacement undergone time v = Δ s Δ t Velocity takes place in a straight line. The unit for velocity is m/s (also written as m.s –1 ). Because displacement is a vector quantity, velocity is also a vector quantity (it has both magnitude and direction). Example 1.3 If an athlete circles a track with a circumference of 400 m in 55 s, calculate his/her: 1. Average speed. 2. Velocity. Solution Given: s = 400 m; t = 55 s 1. v = Δ s Δ t = 400 55 = 7,273 m.s –1 2. v = Δ s Δ t = 0 55 [The displacement is zero because the track is circular] = 0 m.s –1 The athlete’s direction is changing all the time and there can only be momentary velocity. Acceleration and deceleration The rate of change of the velocity of an object is called acceleration or deceleration. In other words, it tells you if the object is speeding up (accelerating) or slowing down (decelerating).

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  Physics

  • Fatih Gozuacik, Denise Pattison, Catherine Tabor(Authors)
  • 2020(Publication Date)
  • Openstax

    (Publisher)

  b. Because the position of a moving object can be defined only when there is a fixed reference frame. 2.1 • Relative Motion, Distance, and Displacement 61 c. Because motion is a relative term; it appears differently when viewed from different reference frames. d. Because motion is always described in Earth’s frame of reference; if another frame is used, it has to be specified with each situation. 2.2 Speed and Velocity Section Learning Objectives By the end of this section, you will be able to do the following: • Calculate the average speed of an object • Relate displacement and average velocity Section Key Terms average speed average velocity instantaneous speed instantaneous velocity speed velocity Speed There is more to motion than distance and displacement. Questions such as, “How long does a foot race take?” and “What was the runner’s speed?” cannot be answered without an understanding of other concepts. In this section we will look at time, speed, and velocity to expand our understanding of motion. A description of how fast or slow an object moves is its speed. Speed is the rate at which an object changes its location. Like distance, speed is a scalar because it has a magnitude but not a direction. Because speed is a rate, it depends on the time interval of motion. You can calculate the elapsed time or the change in time, , of motion as the difference between the ending time and the beginning time The SI unit of time is the second (s), and the SI unit of speed is meters per second (m/s), but sometimes kilometers per hour (km/h), miles per hour (mph) or other units of speed are used. When you describe an object's speed, you often describe the average over a time period. Average speed, v avg , is the distance traveled divided by the time during which the motion occurs. You can, of course, rearrange the equation to solve for either distance or time Suppose, for example, a car travels 150 kilometers in 3.2 hours.

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  A Basic Theory of Everything

  A Fundamental Theoretical Framework for Science and Philosophy

  • Atle Ottesen Søvik(Author)
  • 2022(Publication Date)
  • De Gruyter

    (Publisher)

  With a common currency of, for example, feet or meters, together with numbers, all objects can be compared in size, and a unit of measuring size or space is born. The size of any object or the distance between any objects can now be described as a number expressed in meters. Objects are experienced to move relative to each other. Some motions are constant compared to each other, and some things move faster than others. The earth orbiting the sun moves as fast as the earth takes to spin around itself 365 times, and some can run in one day a distance that others need two days to run. Using many different constant motions that have a constant relation to each other, we can define one constant motion to be used as a measure of all other motions. The thing in motion must cover a distance, which can then be divided into units of time. For example, the earth covering the distance of spinning around its own axis once can be divided into 24 parts called hours, which can be divided into 60 parts called minutes, which can be divided into 60 parts called seconds. With this constant motion giving us units of seconds, minutes, hours, etc., we can now compare all other motions with this motion to describe their speed. The speed will then be a measure of distance divided by time, for example kilometers per hour or meters per second.²⁴⁰ Any speed can be described with a number (in physics called a “scalar”) and meters per second, or m/s.²⁴¹  I am simplifying matters here for pedagogical reasons, since I want the reader to see the development starting with meter and second and then moving to the other concepts. That is why I use the units meter and second for speed and acceleration instead of saying distance div- ided by time. I am also for simplicity just talking about speed here instead of distinguishing be- tween speed and velocity, where velocity is an amount of speed in a direction, while speed only is the numerical value of the velocity.

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  Physics in the Modern World

  • Jerry Marion(Author)
  • 2012(Publication Date)
  • Academic Press

    (Publisher)

  2

  MOTION

  Publisher Summary

  This chapter presents an overview of motion. It describes the motion of automobiles and planets. Acceleration is the change in speed per unit time. The speed of an object at any instant is equal to the slope of the distance–time graph. The acceleration of an object is equal to the slope of the speed–time graph. The chapter illustrates the connection between speed and acceleration. It further illustrates equations for the analysis of motion. When an object is dropped, the gravitational attraction of the earth causes the object to fall with continually increasing speed—the object is accelerated by gravity. The chapter discusses the vertical motion of an object moving freely near the surface of the earth. The vertical and horizontal motions do not affect one another. The chapter explains motion in two dimensions and discusses parabolic motion of an object.

  We live in a restless Universe. Everything around us—from the atoms that make up all matter to automobiles and aircraft to the distant galaxies of stars in space—undergoes motion. Every physical process involves motion of some sort. Because motion is such an important feature of every physical process, it is the logical subject with which to begin our detailed study of physical phenomena. The ideas developed here are used throughout this survey—in describing the motion of automobiles and planets, in discussing electric current, and in studying the behavior of atoms and nuclear particles. Motion is at the heart of every physical process.

  2-1 AVERAGE SPEED

  Distance and Time

  If an object is in one position at a certain time and is in a different position at a later time, we know that movement has occurred. How can we describe the details of movement in a meaningful way? When we take a trip by automobile and note the behavior of the speedometer, we see that we rarely travel very long at constant speed. For one reason or another, it is frequently necessary to slow down or speed up. By the time the trip is completed, we have traveled at many different speeds. But there is still one speed—the average

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  General Engineering Science in SI Units

  The Commonwealth and International Library: Mechanical Engineering Division

  • G. W. Marr, N. Hiller(Authors)
  • 2013(Publication Date)
  • Pergamon

    (Publisher)

  Section 2 Velocity and Acceleration 2.1. Motion When the position of one body relative to another is continuously changing the bodies are said to be in relative motion. Motion, in fact, is always relative. In very many cases we are concerned with the motion of a body relative to the earth, and in such cases the word relative is generally omitted. We are accustomed to refer-ring simply to the motion of a motor vehicle or aircraft. We may say, for example, that a caj* is travelling at a speed of 30 km/h. When we do so, it must be understood that the speed is relative to the earth. 2.2. Velocity The velocity of a body is the rate at which the body is changing its position. Because direction is involved, velocity is a vector quantity. The magnitude, or numerical value, of a velocity is called the speed. The average speed of a body during a given interval of time IS measured by the ratio total distance^raven.d in given time W h e n a body travels equal distances during equal intervals of time, what-ever the magnitude of the time interval, the body is said to travel with constant speed. A velocity may change because of change in speed, or in the direction of motion or because of a change v in both of these. 32 VELOCITY AND ACCELERATION When a body moves in such a way that its velocity does not change, it is said to move with constant, or uniform, velocity. Hence to move with uniform velocity, a body must travel at constant speed in a straight line. EXAMPLE. A vehicle travels a distance of 840 m in 30 sec. Express its average speed in km/h. Distance travelled = 840 m = 0-84 km. 30 s = ai 0-84 km Time interval = 30s = g§öö h = iiö-h .*. average speed — —j = 100-8 km/h. EXAMPLE. The straight-line distance between two towns, A and B, is 49 km. Town A is due north-west from B. The road distance between the towns is 56 km. A motorist leaves A at 13.20 h and arrives at B at 14.10 h. Calculate (a) his average speed; (b) his average velocity.

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  Applied Mechanics

  Made Simple

  • George E. Drabble(Author)
  • 2013(Publication Date)
  • Made Simple

    (Publisher)

  I should add hastily that this is an illus-trative example only. No practising engineer is likely to spend his time in working out such an unlikely quantity as this. But it at least gives rise to the teasing question of what is the true displacement of the rotor, and the even more teasing answer that there is no such quantity. Displacements can only be stated relative to some point in space. For practical engineers, the point is usually a point on the Earth's surface, and for most cases this is assumed to be fixed. Another way of putting this is that, in calculations involving prac-tically all motions of bodies on the Earth, the motion of the Earth itself can be ignored. It is, of course, a very different matter when a journey to the Moon is projected. The Sun then becomes the 'fixed' point. Displacement is not the only quantity where we have to make use of special rules to perform addition. We shall find in Chapter Three that the same rules apply to force. Any quantity that is derived from displacement must also conform—as we are about to discover. Any quantity which requires these special rules of addition is called a vector quantity. (2) Velocity and Speed We have examined the nature of displacement in some detail. As a result, we can be reasonably brief in our examination of velocity, which is the rate of change of displacement. Miles per hour, kilometres per hour, feet per second, metres per second, are examples of the specification of velocity. Since the specification of displacement requires direction as well as magnitude, so must that of velocity. A velocity of 60 kilometres per hour is only half the story: the other half is the direction in which it takes place. The mere magnitude, irrespective of direction, is called the speed. The distinction is important because it means that, if the speed changes, the velocity must change, but the velocity may change without the speed changing.

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  College Physics

  • Michael Tammaro(Author)
  • 2019(Publication Date)
  • Wiley

    (Publisher)

  Hence- forth, when we refer to an object’s velocity, we mean its instantaneous velocity, with the magnitude of the instantaneous velocity being the object’s (instantaneous) speed. 2.4 Solve problems involving average acceleration, velocity, and time. 2.4.1 Interpret or determine the direction of the acceleration. If your friend tells you that her velocity has changed, what she probably means is that the magnitude of her velocity has increased or decreased; that is, the speed with which she is moving has changed. Your friend may use the word acceleration or deceleration when speaking about her changing speed. These words have very specific meanings in physics and, like velocity, the way they are used in everyday conversation is sometimes inconsist- ent with their scientific definitions. When an object’s velocity changes, we say that there is acceleration. Suppose that the velocity changes from v 0 to v in a time t t t 0 ∆ = − . We define the object’s average acceler- ation in the following way: a v t v v t t avg 0 0 = ∆ ∆ = − − (2.4.1) The SI unit of acceleration is / m s 2 . Acceleration is a vector quantity, so it has a magni- tude and a direction, with the direction of the acceleration being the same as the direction of the change in velocity. There is acceleration if there is a change in the direction of the velocity, in the magnitude of the velocity (i.e., the speed), or in both. To illustrate the use of Equation 2.4.1, consider the situation depicted in Animated Figure 2.4.1. A rocket, moving in the positive x direction, is coasting in space at a speed 2.4 ACCELERATION Learning Objectives Animated Figure 2.4.1 A rocket fires its forward thrusters and its speed increases. I N T E R A C T I V E F E A T U R E I N T E R A C T I V E F E A T U R E Acceleration | 51 A car is traveling at a speed of 21.8 m/s. The driver taps the brakes for 3.2 s during which time the magnitude of the average acceleration is 1.5 m/s 2 .

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