One Chapter 2

Motion in a Straight Line

Kinematics - The branch of physics that deals with the description of motion (no forces involved)
Dynamics - The branch of physics that deals with motion and its cause (Force is involved).
To describe motion, we need a reference point.
With respect to this point we consider
Displacement - Change in position where direction is indicated.
- + displacement means the object's position has changed to the right or up.
- an object can have + displacement and still be left or below the reference point because the position has changed to the right or up.
Position - Location WRT reference point.
- direction is important so sign convention applies.
Distance - How far between two point.
- direction is not important.
Displacement and distance show that there are two types of quantities in physics
- Scalars
- Vectors
Scalars - Quantities that can be described with a magnitude and units only.
- e.g. speed, distance, and temperature.
Vectors -Quantities that can be described with a magnitude and units, as well as a direction.
- e.g. velocity, displacement, acceleration, and force.
Vectors can be represented graphically as arrows.
- length of the arrow is proportional to magnitude
- direction of the arrow gives the direction of the vector.
- A scale is needed for these graphical representations.
To report vectors
- symbol has a bar or arrow (->) over it.
- A magnitude is stated including units
direction in included in square brackets after the magnitude

For chapter 2, we use the convention that + means in the same direction as motion and - means in the opposite direction of the motion.
- e.g. Find the displacement of an object that is 18 km left of the reference point and moves to 20 km right of the reference point.

The four step method illustrated above should be followed on all problems which involve numerical answers.

October 28, 2013

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