Wednesday
March 22, 2017

Post a New Question

Posted by on Sunday, April 29, 2012 at 9:07pm.

Two friends are at the local high school track, a circle measuring 440 yards for one complete lap. Abe can jog at 8.2 miles per hour while Bob’s jogging speed is 4.6 miles per hour. If they both start at the same point and jog in the same direction (say clockwise), how many times would they have crossed each other after a half hour? If they started off in opposite directions, what would your answer be?

  • Physics - , Monday, April 30, 2012 at 6:37am

    s = 440 yards = 402.3 m
    v1 = 8.2 mph = 3.7 m/s,
    v2 = 4.6 mph = 2.1 m/s.

    Imagine that B is at rest, then A is jogging at the relative velocity
    v = v1-v2 =3.7 – 2.1 = 1.6 m/s.
    The time of 1 lap motion is
    T = s/v=402.3/1.6 =251 s.
    The number if their meetings is
    N = t/T =0.5•3600/251 =7.17 => 7.
    When they are moving un opposite directions the relative velocity is
    v = v1+v2 = 3.7 +2.1 = 5.8 m/s.
    T = s/v =402.3/5.8 =69.3 s.
    N =t/T =0.5•3600/69.3 = 25.9 => 25

  • Physics - , Monday, April 30, 2012 at 12:16pm

    Thanks a lot Elena

Answer This Question

First Name:
School Subject:
Answer:

Related Questions

More Related Questions

Post a New Question