Question

In a 5.00 km race, one runner runs at a steady 11.7 km/h and another runs at 15.0 km/h. How far from the finish line does the faster runner have to wait at the finish line to see the slower runner cross?

Answer 1

The velocity of the second runner relative to the first is 0.70 km/h faster. The faster runner will win the race if they both run at constant velocity. The distance ahead of the finish line will depend on the time it takes for the slower runner to cross.

Step-by-step explanation:

The velocity of the second runner relative to the first can be found by subtracting the velocity of the first runner from the velocity of the second runner. So, the velocity of the second runner relative to the first is 4.20 km/h - 3.50 km/h = 0.70 km/h faster.

If the front runner is 250 m from the finish line and both runners are running at constant velocity, the faster runner will win the race as their speed is faster. So, the faster runner will cross the finish line first.

The distance ahead that the winner will be when she crosses the finish line can be found by calculating the time it takes for the slower runner to cross the finish line.