Velocity Vs Time Graphs

[kalcorn]

Homework Statement:

This Velocity vs Time graphs models an an object that was ....

Relevant Equations:

None

This is the graph I was given and the answer options. Since the graph is a straight line moving towards the positive direction I thought that meant it was traveling at a constant speed moving in the positive direction. That ended up being the wrong answer. Can anyone offer insight, I missed each question that was like this.

 

[PeroK]

Constant speed means the speed isn't changing. If the speed is constant what is that constant value from the graph?

 

[robphy]

graph is a straight line moving towards the positive direction

graph of what?
what is moving?
What does the graph represent?

 

[Lnewqban]

Homework Statement:: This Velocity vs Time graphs models an an object that was ...
Can anyone offer insight, I missed each question that was like this.

At time=0, the object had a velocity of -8.5 units: the negative sign suggests that the object was moving in a negative direction respect to some pre-set reference.

At time=9 units, the object had a velocity of -3.0 units: the negative sign suggests that the object was still moving in that same negative direction, but slowing down from the previous magnitude of velocity.

 

[David Lewis]

Since the graph is a straight line moving towards the positive direction I thought that meant it was traveling at a constant speed moving in the positive direction

On a position vs time graph, a straight line indicates constant speed.

 

[Halc]

I agree, the straight line (with both numbers increasing) indicates constant speed in a positive direction.
What's missing is labels, so I don't know if it represents a speed of 0.61 or 1.64
Is time vertical or horizontal in that graph? Doesn't say, which is fine because they don't ask.

So your answer seems correct. No idea why they'd say otherwise.

 

[jbriggs444]

I agree, the straight line (with both numbers increasing) indicates constant speed in a positive direction.

On a position versus time graph, that would be correct. This is not a position versus time graph.

 

[Halc]

On a position versus time graph, that would be correct. This is not a position versus time graph.

I stand corrected. The answer given by the OP is wrong, as was I. Both fooled by the same thing.
My comment about the lack of labeling is important now, as it gives different answers depending on which axis is the time and which is the velocity.

 

[hmmm27]

Apparently the student - as well as having to figure out the problem - has to figure out exactly what the problem is, in the first place. Seems to be a pande... umm, forget that.

Anyways...

Having a range from 10 to -10 would seem to indicate that - given the apparent simplicity of the problem - the vertical axis does not indicate Time.

Does that help ?

 

[David Lewis]

The vertical axis is velocity and the horizontal axis is time because the graph is titled Velocity vs Time. (The conventional ordering is "dependent variable" vs "independent variable.")