What Is the Velocity of a Galloping Horse in the First Ten Seconds?

[chinnie15]

Hello,

I am new to physics and am having trouble with this homework problem. I thought I understood it, but it told me I was wrong and I'm not quite sure why. Here is the motion diagram I was given in the homework for the problem:

The question is: What is the horse's velocity during the first ten seconds of its gallop?


Seems easy enough?

I know v=Δx/Δt, and Δx= x_f-x_i, and Δt= t_f-t_i

So, from that I am figuring that the x on the diagram starts at 700m. At 10 seconds, the displacement would be 500-700= -200. The time would be 10 seconds (since it's going from 0s to 10s). Then, the velocity would equal -20m/s. But, the program is telling me that I am incorrect. Am I just reading/interpreting something wrong here? I think I understand, generally, what I'm supposed to be doing?

Thank you so much for any help on this!

 

[HallsofIvy]

You do not have anything labeled "0s" but you have that rightmost dot that is not labeled. Is that "0s"? if so, that corresponds to 600 m, not 700. (700 m is not even on your graph.)

 

[chinnie15]

That is the graph that is given in the problem. I didn't create it. It says this in the problem, above the graph:
The figure shows the motion diagram for a horse galloping in one direction along a straight path. Not every dot is labeled, but the dots are at equally spaced instants of time.

I just assumed that the 'x' (which I assumed was 700m) was where the galloping started? Or is the first dot where the galloping starts? I'm so confused...

 

[chinnie15]

Shoot... just figured it out. That first dot IS the starting place (on 600m), not 'x'. So, it was -10, not -20. Got it now.

Thanks!