• Support PF! Buy your school textbooks, materials and every day products via PF Here!

Position-time graph made with info from a velocity time graph

  • Thread starter jesstryin
  • Start date
8
0
1. Homework Statement

I have been given three velocity-time graphs, and have been asked to use the data from these to create position-time graphs. Each graph represent a route that generally goes south. Changes in direction to go east or west and gradual changes in velocity and time to stop at intersections, and so on, have not been included.

To explain the first velocity/time graph:

70km/h (S) travelled for 5 min, then in no time it jumps to 90km/h (S) from t=5 to t=35, then in no time it switches to 80km/h (S) from t=35 min to t=65 min

2. Homework Equations

I know that distance= time X speed, and velocity is change in position/change in time, so does that mean I use change in position = velocity X change in time?

3. The Attempt at a Solution

5min = 0.083 hours

V X T = 70km/h (s) X 0.083 h = 5.81 km
So, does this mean that at five minutes on the position-time graph, I mark down 5.81 km as the position? And for the second one:

30 min (from t=5 to t=35) = 0.5 hour
90km/h (s) X 0.5h = 45 km

So, do I mark down the first position as 5.81km and the second position as 45km?

If I did this wrong, please tell me the correct equation and show me how to complete this problem so I can learn, I have been trying to teach myself physics and it is hard, so being shown how to complete this problem would help
 
284
41
Yes, that looks right. Another thing to think about when doing these graphs is that since velocity is distance over time, then if you have a position vs. time graph, the slope will be the velocity (i.e. rise over run = position over time). So for example, using the first velocity you could say that the position time graph will have a slope of 70 km/h from 0 to 5 minutes (watch out for units). Doing your calculations gives you the same answer -- this is just another way to think about these problems.
 
8
0
Thanks! I am done making the position-time graphs but need help with the rest of the question. They ask me to record the distance for each route. I know distance = speed X time, but I only have the time, not the speed (the velocity is different from speed I think). Can you tell me what equation to use to record the distance, each route has different sections of the trip that are at different constant velocities.

Also, the last part of the question asks me to measure the displacement from Bradford to Milton using a map, then compare the difference between the distances travelled for each route with the displacement I find. I looked it up, and found that the exact distance is 71.6 km, (driving distance is 85 km according to the same map). Would this be the displacement, or am I doing something wrong?

Thanks again for your help I appreciate it :)
 

Want to reply to this thread?

"Position-time graph made with info from a velocity time graph" You must log in or register to reply here.

Related Threads for: Position-time graph made with info from a velocity time graph

Replies
1
Views
985
Replies
7
Views
109K
Replies
4
Views
365
Replies
6
Views
5K
Replies
2
Views
6K
Replies
3
Views
4K
Replies
3
Views
699
Replies
1
Views
143

Physics Forums Values

We Value Quality
• Topics based on mainstream science
• Proper English grammar and spelling
We Value Civility
• Positive and compassionate attitudes
• Patience while debating
We Value Productivity
• Disciplined to remain on-topic
• Recognition of own weaknesses
• Solo and co-op problem solving
Top