Question on Relative Speed

GRE Quant Problem Solving
1

Question - Albert and Bob are running at constant speeds of 5 meters per second and 8 meters per second, respectively, on a 1-kilometer circular track. If Bob is 300 meters behind Albert, approximately how many minutes will it take for Bob to pass Albert twice?

The solution says that Bob runs faster than Albert at a speed of 3 meter/second. To pass Albert twice, he’ll have to travel 300 meter + 1000 meter. I don’t understand this part. I understand the first time he first crosses Albert is when he catches up and travels 300 meter. But why should he cross Albert only after 1000 m again? Can’t he catch up earlier than that and when?

2

No. So the simplification of relative speed is that because both are running at a constant speed we can pretend that one is static and the other is moving at the speed difference.
In reality, Albert is also moving forward and Bob is also moving but faster by 3m/s.

If Albert and Bob were running in a straight line the distance between them will decrease by 3m/s when Bob is behind and increase at that rate when Bob is ahead.