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C H A P T E R 2Kinematics in One
Dimension
Mechanics
The study of Physics begins with mechanics.
Mechanics
The study of Physics begins with mechanics.
Mechanics is the branch of physics that focuses on the motion of objects and the forces that cause the motion to change.
Mechanics
The study of Physics begins with mechanics.
Mechanics is the branch of physics that focuses on the motion of objects and the forces that cause the motion to change.
There are two parts to mechanics: Kinematics and Dynamics.
Mechanics
The study of Physics begins with mechanics.
Mechanics is the branch of physics that focuses on the motion of objects and the forces that cause the motion to change.
There are two parts to mechanics: Kinematics and Dynamics.
Kinematics deals with the concepts that are needed to describe motion, without any reference to forces.
Chapter 2: Kinematics in one dimensionChapter 3: Kinematics in two dimensions
Mechanics
The study of Physics begins with mechanics.
Mechanics is the branch of physics that focuses on the motion of objects and the forces that cause the motion to change.
There are two parts to mechanics: Kinematics and Dynamics.
Kinematics deals with the concepts that are needed to describe motion, without any reference to forces.
Chapter 2: Kinematics in one dimensionChapter 3: Kinematics in two dimensions
Dynamics deals with the effect that forces have on motion.Chapter 4: Dynamics
Distance and Displacement
Distance and Displacement
Starting from origin, O a person walks 90-m east, then turns around and walks 40-m west.
Distance and Displacement
Starting from origin, O a person walks 90-m east, then turns around and walks 40-m west.
Q: What is the total walked distance?
Distance and Displacement
Starting from origin, O a person walks 90-m east, then turns around and walks 40-m west.
Q: What is the total walked distance? A: 130-m
Distance and Displacement
Starting from origin, O a person walks 90-m east, then turns around and walks 40-m west.
Q: What is the total walked distance? A: 130-m
Q: What is the displacement?
Distance and Displacement
Starting from origin, O a person walks 90-m east, then turns around and walks 40-m west.
Q: What is the total walked distance? A: 130-m
Q: What is the displacement? A: 50-m, due east.
Displacement
position initial ox
position final x
ntdisplaceme oxxx
The displacement Δx is a vector that points from the initial position to the final position. SI Unit of Displacement: meter (m)
2.2 Speed and Velocity
•Average Speed
•Average Velocity
•Instantaneous Velocity
•Instantaneous Speed
Average Speed
Units for speed: m/s, MPH, kmPH.
Average Velocity
ttt o
o
xxx
v
Units for velocity: m/s, MPH, kmPH.
timeElapsed
ntDisplaceme velocityAverage
Instantaneous Velocity and Speed
The instantaneous velocity v indicates how fast an object moves and the direction of the motion at each instant of time.
tt
xv
0lim
The magnitude of the instantaneous velocity is called the instantaneous speed, and it is the number (with units) indicated by the speedometer.
Acceleration
Acceleration
Units: m/s2, cm/s2
Instantaneous acceleration
Acceleration at a particular instant is called instantaneous acceleration.
Deceleration
Deceleration
An object speeds up when the acceleration and velocity vectors point in the same direction.
Deceleration
An object speeds up when the acceleration and velocity vectors point in the same direction.
Whenever the acceleration and velocity vectors have opposite directions, the object slows down and is said to be “decelerating.”
Deceleration
An object speeds up when the acceleration and velocity vectors point in the same direction.
Whenever the acceleration and velocity vectors have opposite directions, the object slows down and is said to be “decelerating.”
Example 4: A drag racer crosses the finish line, and the driver deploys a parachute and applies the brakes to slow down. The driver begins slowing down when t0 = 9.0 s and the car's velocity
is v0 = +28 m/s. When t = 12.0 s, the velocity has been reduced to
v = +13 m/s. What is the average acceleration of the dragster?
Kinematics Equations