2 - Motion in One Dimension

# 2 - Motion in One Dimension - Chapter 2 Motion in One...

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23 Motion in One Dimension CHAPTER OUTLINE 2.1 Position, Velocity, and Speed 2.2 Instantaneous Velocity and Speed 2.3 Acceleration 2.4 Motion Diagrams 2.5 One-Dimensional Motion with Constant Acceleration 2.6 Freely Falling Objects 2.7 Kinematic Equations Derived from Calculus ± One of the physical quantities we will study in this chapter is the velocity of an object moving in a straight line. Downhill skiers can reach velocities with a magnitude greater than 100 km/h. (Jean Y. Ruszniewski/Getty Images) Chapter 2 General Problem-Solving Strategy

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24 Position A s a ﬁrst step in studying classical mechanics, we describe motion in terms of space and time while ignoring the agents that caused that motion. This portion of classical mechanics is called kinematics . (The word kinematics has the same root as cinema . Can you see why?) In this chapter we consider only motion in one dimension, that is, mo- tion along a straight line. We ﬁrst deﬁne position, displacement, velocity, and accelera- tion. Then, using these concepts, we study the motion of objects traveling in one di- mension with a constant acceleration. From everyday experience we recognize that motion represents a continuous change in the position of an object. In physics we can categorize motion into three types: translational, rotational, and vibrational. A car moving down a highway is an example of translational motion, the Earth’s spin on its axis is an example of rota- tional motion, and the back-and-forth movement of a pendulum is an example of vi- brational motion. In this and the next few chapters, we are concerned only with translational motion. (Later in the book we shall discuss rotational and vibrational motions.) In our study of translational motion, we use what is called the particle model we describe the moving object as a particle regardless of its size. In general, a particle is a point-like object—that is, an object with mass but having infinitesimal size. For example, if we wish to describe the motion of the Earth around the Sun, we can treat the Earth as a particle and obtain reasonably accurate data about its orbit. This approximation is justified because the radius of the Earth’s orbit is large com- pared with the dimensions of the Earth and the Sun. As an example on a much smaller scale, it is possible to explain the pressure exerted by a gas on the walls of a container by treating the gas molecules as particles, without regard for the internal structure of the molecules. 2.1 Position, Velocity, and Speed The motion of a particle is completely known if the particle’s position in space is known at all times. A particle’s position is the location of the particle with respect to a chosen reference point that we can consider to be the origin of a coordinate system.
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## This note was uploaded on 02/24/2011 for the course PHYS 102 taught by Professor Wang during the Spring '11 term at Nanjing University.

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2 - Motion in One Dimension - Chapter 2 Motion in One...

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