Answer
a) See the figure below.
b) A car driver was moving at a constant speed of 80 km/h. The driver notices that there is a left 90$^\circ$-curve so he slows his car down at a constant rate to take the curve at a constant speed of 40 km/h. After finishing the curve he starts to speed up again at the same rate until he reached the same speed of 80 km/h.
Work Step by Step
a) See the figure below, and notice that the radial acceleration is always perpendicular to the velocity direction.
b) A car driver was moving at a constant speed of 80 km/h. The driver notices that there is a left 90$^\circ$-curve so he slows his car down at a constant rate to take the curve at a constant speed of 40 km/h. After finishing the curve he starts to speed up again at the same rate until he reached the same speed of 80 km/h.
