Calculating acceleration due to gravity on a planet

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The discussion revolves around calculating the acceleration due to gravity using data from a graph. The initial velocity is stated as 31 m/s, with a horizontal velocity of 21 m/s and a travel time of 5 seconds, leading to a total distance of 105 m. The user initially calculated the vertical velocity as 22.8 m/s but miscalculated the acceleration due to gravity, arriving at -9.12 m/s². After clarification, the correct value was found to be +9.12 m/s², although the user expressed confusion about why the result is positive. The conversation emphasizes the importance of accurately interpreting graph data in physics calculations.
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Homework Statement



The data is taken from a graph. The initial velocity is 31m/s. I found the horizontal velocity to be 21m/s. The time the ball travels is 5 seconds. The total distance the ball traveled is 105m. The ball lands at the same vertical level at which it starts. Air resistance can be neglected.


Homework Equations



Im pretty sure I have to use this equation, where t= 2.5.

v = v(initial) + at

I used the pythagoreum theorem to find the initial vertical velocity to be 22.8m/s. Then divided it by 2.5. What I came up with, -9.12, which is wrong.

I just can't find the acceleration due to gravity. It looks straight forward but I am missing a step. Any ideas?

Thanks!
 
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Your method appears to be correct and the answer follows from the numbers that you gave. If the answer is incorrect, then you need to make sure that you read the graph correctly. When you say "the initial velocity is 31 m/s", you mean the initial speed is 31 m/s, right?
 
Here is a link to the graph, which plots the velocity over time (sorry i didnt think to add it)

https://wug-s.physics.uiuc.edu/cgi/courses/shell/common/showme.pl?cc/DuPage/phys2111/fall/homework/Ch-03-04/golfball_plot/golfball_plot-1.jpg

Thanks for the help!
 
Last edited by a moderator:
Ahh, it was +9.12. However, I am not sure as to why it is positive.
 

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