IB Maths AA/AI HL. Lines. Vectors. Ex. 6. Application in kinematics. Nov15 2-10.

Ed walks in a straight line from point P(−1, 4) to point Q(4 , 16) with constant speed.
Ed starts from point P at time t = 0 and arrives at point Q at time t = 3, where t is
measured in hours.
Given that, at time t, Ed’s position vector, relative to the origin, can be given in the form,
r = a + tb,
(a) find the vectors a and b.
Roderick is at a point C(11 , 9). During Ed’s walk from P to Q Roderick wishes to signal
to Ed. He decides to signal when Ed is at the closest point to C.
(b) Find the time when Roderick signals to Ed.