Chapter 2 Section 1: Describing Motion - Physics

Frame of reference

an arbitrary system to which an object is compared to describe its motion.

One thing common to all moving objects

a change in position with respect to another object.

Straight line motion is a

simple example of motion

Straight line motion

follows a path directly between two points without turning left or right

The description of motion is a description of

time and place

2 FACTORS you must know to describe the motion of an object along a STRAIGHT LINE is

Where an object is located and when it is at that position.

Time Interval

A measurement that should be the same between one image and the next using a series of images

Motion Diagram

A figure showing the position of a moving object at equal time intervals

Particle Modles

model in which you replace each object under study with a single point

To use a particle model to describe motion, the object’s size must be…

much less than the distance it moves

A particle model is made by

Choosing a location for the object; place a point over the location at the end of each time interval

Origin

The point at which both variables in a coordinate system have the value zero

Coordinate Systems

system used to describe motion that gives the zero point location of the variable being studied and the direction in which the values of the variable increase

Position

The distance and direction from the origin to an object

Distance

The length of an object’s path, even if the object moves in many directions

Negative position

Located to the left or below the origin

magnitude

a measure of size

Vector

has both magnitude and direction, a quantity

Scalar

a quantity, such as temperature or distance, a number with no direction

Vector vs Scalar

Scalar only has magnitude. A vector has magnitude and direction

Time intervals are

scalars

Time interval

difference between two times

Position and Displacement are

Vectors

Four vectors are…

velocity, acceleration, momentum, and position

Position

A vector with an arrows tail and the origin of a coordinate system and the arrows tip at the place

Displacement equals…

the final position minus the initial

Resultant

A vector that represents the sum of TWO other vectors; it always points from the first vector to the last vector’s tip

When adding vectors…

use plus and minus signs to indicate direction and then add