A runner of mass 51.5 kg starts from rest and accelerates with a constant acceleration of 1.35 m/s2 until she reaches a velocity of 5.7 m/s. She then continues running with this constant velocity. (Take the direction the runner is going to be the positive direction. Indicate the direction with the sign of your answer.)

Question

A runner of mass 51.5 kg starts from rest and accelerates with a constant acceleration of 1.35 m/s2 until she reaches a velocity of 5.7 m/s. She then continues running with this constant velocity. (Take the direction the runner is going to be the positive direction. Indicate the direction with the sign of your answer.)
(a) How far has she run after 64.7 s?
(b) What is the velocity of the runner at this point?

bobpursley · Answer

do this in two parts: distance running speeding up vf=vi+2at solve for t, then distance= vf/2 * t second runnign at constant velocity distance= vf*(64.7-t) add the distances.