23.7k views
1 vote
Runner A is initially 2.0 km west of a flagpole and is running with a constant velocity of 2.8 km/h due east. Runner B is initially 4.0 km east of the flagpole and is running with a constant velocity of 2.0 km/h due west. What will be the distance of the two runners from the flagpole when their paths cross?

A. 6.0 km from the flagpole due east
B. 2.0 km from the flagpole due west
C. 8.0 km from the flagpole due east
D. 2.0 km from the flagpole due east

1 Answer

4 votes

Final answer:

The distance of Runner A from the flagpole when their paths cross is 1.5 km. Since Runner B is running west, the distance of Runner B from the flagpole is also 1.5 km. Therefore, the correct answer is: D. 2.0 km from the flagpole due east

Step-by-step explanation:

Let's analyze the situation:

1. Runner A starts 2.0 km west of the flagpole and runs east at a speed of 2.8 km/h.

2. Runner B starts 4.0 km east of the flagpole and runs west at a speed of 2.0 km/h.

Let t be the time it takes for the runners to meet.

The position of Runner A as a function of time is given by x_A = -2.0 + 2.8t (initial position minus distance covered as he runs to the east).

The position of Runner B as a function of time is given by x_B = 4.0 - 2.0t (initial position plus distance covered as he runs to the west).

To find the time t when the runners meet, set x_A = x_B:

-2.0 + 2.8t = 4.0 - 2.0t

Combine like terms:

4.8t = 6.0

t = 6.0/4.8

t = 1.25

Now, substitute t = 1.25 hours into either x_A or x_B to find the distance from the flagpole:

x_A = -2.0 + 2.8(1.25)

x_A = -2.0 + 3.5

x_A = 1.5 ,km

So, the distance of Runner A from the flagpole when their paths cross is 1.5 km. Since Runner B is running west, the distance of Runner B from the flagpole is also 1.5 km. Therefore, the correct answer is: D. 2.0 km from the flagpole due east

User Gabriel Osorio
by
7.8k points