What is the relationship between velocity and time on this graph?

In summary: This Velocity vs Time graphs models an object that was moving in a certain direction at a certain time.The student thought that because the graph was moving in a positive direction, the object was traveling at a constant speed. However, this was not the case.The graph is a straight line with both numbers increasing, indicating that the speed is increasing.Since the graph is a straight line moving towards the positive direction, the student thought that meant the object was traveling at a constant speed. However, this was not the case.
  • #1
kalcorn
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Homework Statement
This Velocity vs Time graphs models an an object that was ....
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Screen Shot 2020-05-20 at 3.26.32 PM.png
Screen Shot 2020-05-20 at 3.26.26 PM.png

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.
 

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  • #2
Constant speed means the speed isn't changing. If the speed is constant what is that constant value from the graph?
 
  • #3
kalcorn said:
graph is a straight line moving towards the positive direction
graph of what?
what is moving?
What does the graph represent?
 
  • #4
kalcorn said:
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.
 
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  • #5
kalcorn said:
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.
 
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  • #6
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.
 
  • #7
Halc said:
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.
 
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  • #8
jbriggs444 said:
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.
 
  • #9
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 ?
 
  • #10
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.")
 
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1. What is velocity?

Velocity is a measure of an object's speed and direction of motion. It is a vector quantity, meaning it has both magnitude (speed) and direction.

2. How is velocity represented on a graph?

Velocity is typically represented on a graph by plotting it on the y-axis and time on the x-axis. The slope of the line on the graph represents the object's velocity.

3. What does the slope of the line on the graph represent?

The slope of the line on the graph represents the object's velocity. A steeper slope indicates a higher velocity, while a flatter slope indicates a lower velocity.

4. What is the relationship between velocity and time on this graph?

The relationship between velocity and time on this graph is that velocity is directly proportional to time. As time increases, velocity also increases, and vice versa.

5. How can we calculate velocity from a graph?

To calculate velocity from a graph, we can find the slope of the line connecting two points on the graph. The slope is equal to the change in velocity over the change in time, which can be calculated by dividing the difference in the y-values by the difference in the x-values.

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