Chapter 2
Motion in one dimension
2.1 Describing motion
2.2 Uniform motion
2.3 Instantaneous velocity
2.4 Acceleration
2.5 Motion with constant acceleration
2.6 Solving one-dimensional motion problems
2.7 Free fall
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2.1 Describing motion
To begin the description of an object’s position, you have to :
●
choose a coordinate system (direction and units)
●
make a drawing (particle model)
position
Example: motion diagram (student walking to school)
To complete the description of an object’s position, you can:
●
make a table of data (optional, not necessary)
●
make a position-versus-time graph
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From the particle model to a continuous curve:
●
a graph is not a drawing
●
a graph is an abstract representation of motion
●
velocity can be deduced from a position-vs-time graph
●
position can be deduced from a velocity-vs-time graph
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Velocity is a vector:
●
a magnitude (units).
●
a direction (with respect to a coordinate system).
●
dimension of velocity (and speed): LT
-1
.
●
units of velocity (and speed): m/s, mi/hr, km/hr, ….
Velocity:
a vector
O
y
j
v
1
v
2
An object is moving with velocity v
1
.
Another object is moving with velocity v
2
.
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