Calculating Velocity of Bowling Ball at 3.0s

[Allura]

[PLAIN]http://lc.cit.jmu.edu/cgi-bin/plot.png?file=safavifn_jmu_1283628193_8083304_plot.data
I've been trying to figure out this problem but for some reason I can't get the right answer. I'm not sure if I'm reading the graph values wrong or if I'm using the wrong formula.

1. A bowler rolls a bowling ball down a lane. A plot of the position versus time graph is shown. What is the velocity (in m/s) of the bowling ball at 3.0 seconds?



2. I thought it would just be the slope, so s = rise/run, so s = 7m/3s or s = 6m/3s



3. I keep getting 2.3 m/s

I know this is an easy question, I just can't get it =( I've tried playing around with the x and y values, I've tried using the book examples, I tried notes examples, I've tried asking my friends who've taken physics before -This problem is driving me insane.

 

[mplayer]

Your approach seems correct, I think that maybe the values you are reading off the graph are a bit inaccurate. The value you have for time, t=3s, is good, since that is given, but I would say that the distance the ball has traveled at t=3s is closer to 7.5m or 8m rather than the 7m that you used in your calculation. Hope this helps.

 

[Allura]

It was 7.5, thanks!