Physics

posted by .

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 -

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 -

Thanks a lot Elena

Similar Questions

1. Math [urgent]

1. The sum of three numbers is 301. The second number is 3 less than twelve times the first number. The third number is 4 more than seven times the number. Find the three numbers. ~~~~~~ 2. Two friends live 15 miles apart. One day …
2. Math

Jesse jogs at a rate of 6 miles per hour. The next time she jogs, she increases her speed to 7 miles per hour. How long will it take her to jog 6 miles?
3. Math

You walk at 4 miles per hour for 1/2 hour, and then jog at 6 miles per hour for h hours. The total distance that you cover both walking and jogging is 6 miles. Write an equation that represents this situation.
4. maths

A motorist travels 120 miles to his destionation at an average speed of 60 miles per hour and returns to the starting point at an average speed of 40 miles per hour.His average speed for the entire trip is 1. 53 miles per hour 2. 52 …
5. arithmetic

if A and B ARE MOVING IN a circular track of length 0.32miles from the start line whose speed are 7 miles per hour and 9 miles per hour respectively ,then after how many seconds will they meet for the first time?
6. math

the track at our school is 440 yards long. it took Maya 10 minutes to jog around the track 4 times. find her speed in miles per hour. I first found out that r=d/t then we converted minutes to hour. we got 24 times around the track
7. Trigonometry- Help!

After one hour in flight, an airplane is located 200 miles north and 300 miles west of the airport. What is the magnitude of the plane's velocity?
8. pre-calc

Alice walks on a straight line at four miles per hour. Two hours after she begins walking, Bob runs after her at a rate of six miles per hour. How fast (in miles per hour) is Bob gaining on Alice?
9. pre-calc

Alice walks on a straight line at four miles per hour. Two hours after she begins walking, Bob runs after her at a rate of six miles per hour. How fast (in miles per hour) is Bob gaining on Alice?
10. Pre-calc

Alice walks on a straight line at four miles per hour. Two hours after she begins walking, Bob runs after her at a rate of six miles per hour. How fast (in miles per hour) is Bob gaining on Alice?

More Similar Questions