# Problem 2-99 - v-t graph - Part 9 - (b)

Two cars, A and B, are stopped for a red light beside each other at an intersection. The light turns green and the cars accelerate. Their velocity time graphs are shown in Figure 2 44. (The positive direction is "forward.")

(a) At what time(s) do A and B have the same velocity?

(b) When does B overtake A? (Hint: Their displacements must be equal at that time and displacement can be found from a velocity time graph.)

(c) How far have the cars traveled when B overtakes A?

Accumulated Solution

The velocities are equal at \(\mathrm{t = 45\; s}\)

\(\mathrm{d_{A,60} = (1/2)(15\;m/s)(30\;s) + (15\;m/s)(30\;s) = 675\; m}\)

\(\mathrm{d_{B,60} = (1/2)(20\;m/s)(60\;s) = 600\; m}\)

\(\mathrm{d_{A,60} - d_{B,60} = 75 \;m}\)

\(\mathrm{v_{B,A}= 5\; m/s}\)

No. Check the units.