《大学物理》课程PPT教学课件：（英文版）Chapter 2 Motion in One Dimension

Chapter 2 Motion in one dimension

Chapter 2 Motion in One Dimension

Dynamics The branch of physics involving the motion of an object and the relationship between that motion and other physics concepts Kinematics is a part of dynamics In kinematics, you are interested in the description of motion Not concerned with the cause of the motion

Dynamics ◼ The branch of physics involving the motion of an object and the relationship between that motion and other physics concepts ◼ Kinematics is a part of dynamics ◼ In kinematics, you are interested in the description of motion ◼ Not concerned with the cause of the motion

Quantities in Motion Any motion involves three concepts Displacement Velocity Acceleration These concepts can be used to study objects in motion

Quantities in Motion ◼ Any motion involves three concepts ◼ Displacement ◼ Velocity ◼ Acceleration ◼ These concepts can be used to study objects in motion

Brief History of Motion Sumaria and egypt Mainly motion of heavenly bodies Greeks also to understand the motion of heavenly bodies Systematic and detailed studies Geocentric model

Brief History of Motion ◼ Sumaria and Egypt ◼ Mainly motion of heavenly bodies ◼ Greeks ◼ Also to understand the motion of heavenly bodies ◼ Systematic and detailed studies ◼ Geocentric model

Modern ideas of motion Copernicus Developed the heliocentric system a Galileo Made astronomical observations with a telescope Experimental evidence for description of motion Quantitative study of motion

“Modern” Ideas of Motion ◼ Copernicus ◼ Developed the heliocentric system ◼ Galileo ◼ Made astronomical observations with a telescope ◼ Experimental evidence for description of motion ◼ Quantitative study of motion

2.1 displacement D2002 Brooks Cole Publishing-a division of Thomson Learning Position Defined in terms of a frame of reference One dimensional so generally the X- or y-axis Defines a starting ol point for the motion

2.1 displacement Position ◼ Defined in terms of a frame of reference ◼ One dimensional, so generally the x￾or y-axis ◼ Defines a starting point for the motion

Displacement Defined as the change in position △X≡X-X f stands for final and i stands for initial May be represented as ay if vertical Units are meters(m) in SI centimeters (cm)in cgs or feet (ft)in US Customary

Displacement ◼ Defined as the change in position ◼ ◼ f stands for final and i stands for initial ◼ May be represented as y if vertical ◼ Units are meters (m) in SI, centimeters (cm) in cgs or feet (ft) in US Customary f i   − x x x

Displacements -40 10 x(m) 50 10 0 (m) e2008 Bracks cole. Thomson

Displacements

Vector and scalar Quantities Vector quantities need both magnitude(size)and direction to completely describe them Generally denoted by boldfaced type and an arrow over the letter t or- sign is sufficient for this chapter Scalar quantities are completely described by magnitude only

Vector and Scalar Quantities ◼ Vector quantities need both magnitude (size) and direction to completely describe them ◼ Generally denoted by boldfaced type and an arrow over the letter ◼ + or – sign is sufficient for this chapter ◼ Scalar quantities are completely described by magnitude only

Displacement Isn't Distance The displacement of an object is not the same as the distance it travels Example: Throw a ball straight up and then catch it at the same point you released it The distance is twice the height The displacement is zero

Displacement Isn’t Distance ◼ The displacement of an object is not the same as the distance it travels ◼ Example: Throw a ball straight up and then catch it at the same point you released it ◼ The distance is twice the height ◼ The displacement is zero