Is my work correct? (Two students running on a track)

  • #1
bekishe004
11
2
Homework Statement
I am not sure if my working out is correct because I have 2 values
Relevant Equations
d=vt
Two students run around a 400m sport field. A goes anticlockwise (i.e., 1-2-3-4-1) while Bruns clockwise (i.e., 1-4-3-2-1). Students A and B can run 400 m in 75.0 s and 65.0 s,respectively.

1695871185990.png

Students A and B should meet at some point of the run. Where do they meet? Assume the cross-over position is P. What is their relative velocity at position P.
My working out:

Lets first find the relative velocity, which going to be 12

t=d/v
400/12 = 33.33... seconds

d = 5.33 * 33.33 = 177.67m
d= 6.67 * 33.33 = 222.32m

Now, whats confusing me is that I have two values and I am not sure what to do with them.

Any help will be appreciated :)
 
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  • #2
I hope this time and I haven't violated any rules.
 
  • #3
bekishe004 said:
I hope this time and I haven't violated any rules.
I don't think so. How do you know that the relative velocity is "12"? 12 what? What are 5.33 and 6.67 and how did you get them?

Suppose you cut the track at point 1 and you straighten it out to get a straight 400-m track. The runners start at each end going towards each other. Do you see where this is going?
 
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  • #4
kuruman said:
I don't think so. How do you know that the relative velocity is "12"? 12 what? What are 5.33 and 6.67 and how did you get them?

Suppose you cut the track at point 1 and you straighten it out to get a straight 400-m track. The runners start at each end going towards each other. Do you see where this is going?
Sure,

Student A v=d/t= 400/75=5.33m/s
Student B v=d/t=400/65=6.15m/s

It appears I made a mistake, its not 6.67 but 6.15m/s my bad

"Suppose you cut the track at point 1 and you straighten it out to get a straight 400-m track. The runners start at each end going towards each other. Do you see where this is going?"
Not really sorry
 
  • #5
bekishe004 said:
Not really sorry
In the oval track, the runners start and meet at point P such that the sum of their distances from their respective starting points is 400 m.

In the straight track, the runners start and meet at point P such that the sum of their distances from their respective starting points is 400 m.

If you can find P in the straight track case, you have found point P in the oval track case.

Now do you see?
 
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  • #6
Ohhh
kuruman said:
In the oval track, the runners start and meet at point P such that the sum of their distances from their respective starting points is 400 m.

In the straight track, the runners start and meet at point P such that the sum of their distances from their respective starting points is 400 m.

If you can find P in the straight track case, you have found point P in the oval track case.

Now do you see?
 
  • #7
kuruman said:
In the oval track, the runners start and meet at point P such that the sum of their distances from their respective starting points is 400 m.

In the straight track, the runners start and meet at point P such that the sum of their distances from their respective starting points is 400 m.

If you can find P in the straight track case, you have found point P in the oval track case.

Now do you see?
With my new values and understanding,

this what I am getting

5.33t+6.15t=400
11.48x=400
x=400/11.48

400/11.48 = 34.84s

5.33*34.84 = 185.70
6.15*34.84 = 214.27

sum of two these values gives 400m

I still kinda confused where I go from here
 
  • #8
bekishe004 said:
With my new values and understanding,

this what I am getting

5.33t+6.15t=400
11.48x=400
x=400/11.48

400/11.48 = 34.84s

5.33*34.84 = 185.70
6.15*34.84 = 214.27

sum of two these values gives 400m

I still kinda confused where I go from here
I don't think I am wrong because when Student A travels to 214m thats where Student B who has travelled 185 m.
 
  • #9
I want to thank everyone who has helped me or trying too.

I did pretty well in chemistry and precalc but I dunno why physics is kicking my butt
 
  • #10
bekishe004 said:
With my new values and understanding,

this what I am getting

5.33t+6.15t=400
11.48x=400
x=400/11.48

400/11.48 = 34.84s

5.33*34.84 = 185.70
6.15*34.84 = 214.27

sum of two these values gives 400m

I still kinda confused where I go from here
Answer the question. Where is point P?
 
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  • #11
bekishe004 said:
I still kinda confused where I go from here
Student B is faster than student A.
Therefore, when B completes 400 m, he will be at point 1 again, but student A has not reached point 1 yet (he may be moving between points 4 and 1).

The meeting time must be the same for A and B and its value should be between 65 and 75 seconds.

You could create a distance versus time diagram for both students in order to visualize the relative movements more clearly.
 
Last edited:
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  • #12
kuruman said:
Answer the question. Where is point P?
I am unsure

but am I close?
 
  • #13
Lnewqban said:
Student B is faster than student A.
Therefore, when B completes 400 m, he will be at point 1 again, but student A has not reached point 1 yet (he may be moving between points 4 and 1).

The meeting time must be the same for A and B and its value should be between 65 and 75 seconds.

You could create a distance versus time diagram for both students in order to visualize the relative movements more clearly.
I have tried that it didnt help me out

1695877871686.png
 
  • #14
Can you answer where they meet if on a straight track?
 
  • #15
bekishe004 said:
I have tried that it didnt help me out

View attachment 332720
Your graph is as though they go the same direction around. Try reversing one.
 
  • #16
haruspex said:
Your graph is as though they go the same direction around. Try reversing one.
Can you help me with that please?
I know that y=6.15x
and y=5.33x
I am so confused
 
  • #17
haruspex said:
Your graph is as though they go the same direction around. Try reversing one.
1695885773882.png

This might be it
I apologise for being slow
Again, thank you to everyone for helping me
 
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FAQ: Is my work correct? (Two students running on a track)

1. How do I determine if the students are running at a constant speed?

To determine if the students are running at a constant speed, you can measure the time it takes for them to complete each lap and see if it remains consistent. If the time for each lap is the same, then they are running at a constant speed.

2. What factors should I consider when comparing the performance of the two students?

When comparing the performance of the two students, consider factors such as their lap times, the total distance covered, their running form, and any external conditions like weather or track surface. Additionally, take into account their starting point and whether they maintained their speed throughout the run.

3. How do I calculate the average speed of each student?

To calculate the average speed of each student, divide the total distance they ran by the total time they took. The formula is: Average Speed = Total Distance / Total Time. Ensure that the units of distance and time are consistent.

4. What can cause discrepancies in the lap times between the two students?

Discrepancies in lap times can be caused by various factors such as differences in physical fitness, running strategy, pacing, fatigue, and environmental conditions. Additionally, individual variations in motivation and experience can also play a role.

5. How can I ensure the accuracy of my measurements and data collection?

To ensure the accuracy of your measurements and data collection, use reliable timing devices, measure the track accurately, and record the data meticulously. It may also help to have multiple observers and use video recordings for precise timing. Consistency in the method of measurement is key to obtaining accurate results.

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