How do you determine the direction of
the acceleration from vx vs. t and vy vs. t graphs?
A vx
vs t graph describes the horizontal component of a motion only.� No information about the vertical component
of a motion can be gleaned from a vx vs. t
graph.� The opposite is true for a vy vs. t graph.�
No information about the horizontal component of a motion can be gleaned
from a vy vs. t graph.�
On a vx
vs. t graph, the slope is equal to the x-component of the acceleration.�
� A
vx vs. t graph with positive slope has
positive ax.�
� A
vx vs. t graph with negative slope has
negative ax.�
� A
vx vs. t graph with zero slope has zero ax.�
Similar rules govern a vy vs. t graph where the slope is equal to the
y-component of the acceleration.�
� A
vx vs. t graph with positive slope has
positive ay.�
� A
vx vs. t graph with negative slope has
negative ay.�
� A
vx vs. t graph with zero slope has zero ay.�
f
The acceleration selector
is a graph of ay vs. ax.�
The selector only has one choice for the magnitude of the acceleration
in each direction.� Hence, knowing the
signs of ax and ay is sufficient for selecting the
correct acceleration.�