- #1

neon612

- 5

- 0

This is homework help, but I think all I need to learn is how to read a VT graph properly. My professor uses MasteringPhysics.com and this is one of the questions from the site. The way it works is: the student has 5 attempts to answer a question before it is counted wrong and I'm down to my last attempt. I'm hoping I've already figured out the right answer and I just need to make sure that what I think is the right answer actually is.

After each attempt it gave me some feedback saying "The location of the cars are unknown at this time. All that is known is their velocities." And that was for points A, B, C, and E.

Two cars travel on the parallel lanes of a two lane road. The cars' motions are represented by the velocity versus time graph. Answer each of the questions with reference to the lettered times (A through E) marked on the graph. (graph attached)

http://img703.imageshack.us/img703/633/1011351.jpg [Broken]

At which of the lettered times, if any, do the two cars pass?

From my textbook and searching the net I've been able to figure out:

The two cars have the same velocity at point D

Car 1 stops at point B

Car 2 stops at point E

If I think about it as a east-west road, I come up with:

Car 1 is traveling west and slowing down until it gets to point B. Then it accelerates, heading east.

Car 2 is traveling west and slowing down until half a graph square before A. Then it speeds up heading east until point C, when it starts slowing down until point E. It stops at point E, and speeds up heading west.

I know the area under the curve will tell me the displacement. But how does that work if I'm not given any numbers to work with?

So, I guess the answer I keep coming up with is that the problem doesn't have enough information to figure an exact position. (To put it in the wording from Mastering Physics "Cannot be Determined")

After each attempt it gave me some feedback saying "The location of the cars are unknown at this time. All that is known is their velocities." And that was for points A, B, C, and E.

## Homework Statement

Two cars travel on the parallel lanes of a two lane road. The cars' motions are represented by the velocity versus time graph. Answer each of the questions with reference to the lettered times (A through E) marked on the graph. (graph attached)

http://img703.imageshack.us/img703/633/1011351.jpg [Broken]

At which of the lettered times, if any, do the two cars pass?

## The Attempt at a Solution

From my textbook and searching the net I've been able to figure out:

The two cars have the same velocity at point D

Car 1 stops at point B

Car 2 stops at point E

If I think about it as a east-west road, I come up with:

Car 1 is traveling west and slowing down until it gets to point B. Then it accelerates, heading east.

Car 2 is traveling west and slowing down until half a graph square before A. Then it speeds up heading east until point C, when it starts slowing down until point E. It stops at point E, and speeds up heading west.

I know the area under the curve will tell me the displacement. But how does that work if I'm not given any numbers to work with?

So, I guess the answer I keep coming up with is that the problem doesn't have enough information to figure an exact position. (To put it in the wording from Mastering Physics "Cannot be Determined")

Last edited by a moderator: