Key Terms
Kinematics
Study of motion without considering causes
Position
Location of an object at a particular time
Reference frame
The fixed (or moving) point you measure from. A person on a plane uses the plane as a reference frame, not the ground.
Displacement (delta-x)
Change in position.
Formula
A-bar = delta-v / delta-t = (v - v_0) / t
Distance
Magnitude of displacement; scalar
Distance traveled
Total path length; scalar
Example
Drive 3 km to the store and back in 30 min.
Vector
Magnitude and direction
Scalar
Magnitude only; no direction
Elapsed time
Delta-t = t_f - t_i
Convention in this chapter
T_0 = 0, so elapsed time = t.
Formally
Average velocity over an infinitesimally small time interval.
Acceleration
Rate of change of velocity; vector; units m/s^2
Speeding up
Acceleration and velocity have the SAME sign. Slowing down: acceleration and velocity have OPPOSITE signs.