Conceptual Physics by HewittC H A P T E R   2-

Linear Motion

http://www.youtube.com/watch?v=hz65AOjabtM

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:Linear Motion-- Kinematics in one dimensionChapter 3:Projectile Motion-- 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 5 primarily

Position vs Distance vs Displacement

• Position is the location of an object at any given time along a chosen path with a chosen position selected as 0.

• At time 0, an object may be at any position along the chosen path.

• In a race between a child and a parent, the parent may give the child a head start, say at position 5 meters, whereas the parent starts at position 0 meters on the race path.

Position vs Distance vs Displacement

• Distance is most correctly interpreted to mean the total length travelled.

• If school is 3 miles from your home, the total distance you travel in a day is 6 miles (assuming you only are at school or home).

Position vs Distance vs Displacement

• Displacement is simply the final position minus the initial position which is often represented by the equation:

D = xf-xi

• So as in the previous slide, if school is 3 miles from your home, the total displacement for you that day is 0 miles since you end up where you started.

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)

Final Note and Additional Resource

http://www.physicsclassroom.com/class/1dkin/u1l1c.cfm

http://www.physicsclassroom.com/class/1dkin/u1l1c.cfm

Distance is a scalar quantity (only magnitude).

Displacement is a vector quantity (magnitude and direction).