Imagine that you traveled back in time to the Fourth of July, 1999. You are at Stanford Stadium, watching the semifinal of the W
omen's World Cup soccer match. Mia Hamm, star of the United States team, has just received the ball on a breakaway. She is 60 yards from Brazil's goal. Brazilian star Sissi is the closest opponent to Hamm and is 10 yards behind her. Mia takes off for Brazil's goal and, while dribbling the ball, is able to run at a speed of 6.8 yards per second. Sissi takes off at the same time as Hamm and runs at 8.4 yards per second. (She is able to run faster because she isn't dribbling the soccer ball.) Hamm has decided to shoot at the exact moment that Sissi catches up to her, because at that point it will still be difficult for Sissi to block the shot when she is side by side with Hamm. How far away from the goal will Hamm be when she shoots
Speed is the ratio of distance to time. It is given by the formula:
Speed = distance / time
Mia Hamm is running at a speed of 6.8 yards per second. Let us assume that Mia covers a distance (d) during time (t) when Sissi catches up to her. Hence:
6.8 = d / t
t = d / 6.8
Sissi was 10 yards behind Mia Hamm and running at 8.4 yards per second. Therefore:
8.4 = (d + 10) / t
t = (d + 10)/ 8.4
d / 6.8 = (d + 10)/ 8.4
8.4d = 6.8d + 68
1.6d = 68
d = 42.5 yards
Mia had covered 42.5 yards when Sissi catches up with her. Therefore Mia Hamm distance to goal = 60 yards - 42.5 yards = 17.5 yards
