13.15 13.5: SUMMARY

• For an object whose path is described by a vector-valued function r(t),

  

• The velocity vector v(t) points in the direction of motion. Its length υ(t) = ∥v(t)∥ is the object’s speed.

• The acceleration vector a is the sum of a tangential component (reflecting change in speed) and a normal component (reflecting change in direction):

  a(t) = a_T(t)T(t) + a_N(t)N(t)