# Problem P. 4003. (October 2007)

**P. 4003.** On a running training the runners run at a speed of *v*=5 m/s along a straight path, forming an *L*=35 m long column. Their coach runs towards them at a speed of *u*=2 m/s. The first runner turns back and runs in the same direction as the coach, still at a speed of *v*, when he meets the coach, and so do all the runners when they meet their coach.

*a*) How much time elapses between the turn of the first and the last runner?

*b*) How long is the column when they all run in the same direction as the coach?

(4 pont)

**Deadline expired on November 12, 2007.**

### Statistics:

366 students sent a solution. 4 points: 229 students. 3 points: 15 students. 2 points: 108 students. 1 point: 7 students. 0 point: 2 students. Unfair, not evaluated: 5 solutions.

Problems in Physics of KöMaL, October 2007