Chapter 2 - Representing Motion
2-1 Picturing Motion
• All kinds of motion (changes in position)
>
Motion diagrams - a series of images showing the
positions of a moving object at equal time intervals
>
Particle model - replace the object from a motion
diagram with a central point
–
to use:
«
the object's size must be much less than the
distance it moves
Glencoe Physics 2013
Glencoe Physics 2013
2-2 Where and When
• Coordinate System - gives the location of the zero point
of the variable you are studying and the direction in
which the values of the variable increase
>
Try to imagine every physics problem on a graph
>
origin - the point at which all variables in a
coordinate system have a zero value
>
position - the distance and direction from the origin
to the object
>
distance - the entire length of an object's path,
even if it moves in many directions
>
Can position be negative?
–
Sure!
Glencoe Physics 2013
• Vector - a quantity that has both magnitude and
direction
• Scalar - a quantity that is just a number without any
direction
• time interval
>
∆t = tf - ti
>
The runner's time is scalar, but what about the
runner's position?
>
You can draw an arrow from the origin to the
runner's current location. The arrows have both
magnitude and direction (makes them vectors)
>
Position and displacement are both vectors
>
Displacement - a change in position
>
∆x = xf - xi
Glencoe Physics 2013
Glencoe Physics 2013
• Adding and subtracting vectors
>
resultant - a vector that represents the sum of two
vectors
Glencoe Physics 2013
Homework:
P 36 # 2,3
P 40 # 7,10
P 54 # 46,47