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Calculating acceleration of gravity on a planet

1. Homework Statement
An astronaut on a strange planet finds that he can jump a maximum horizontal distance of 30m if his initial speed is 9m/s. What is the acceleration of gravity on the planet?

2. Homework Equations
Vf^2=Vi^2+2a(Xf-Xi)

3. The Attempt at a Solution
I used the formula mentioned above, plugged in number
Vf=0m/s
Vi=9m/s
X=Xf-Xi=30m
and get a=-1.35m/s^2

I'm not sure if it is correct, could someone double check and tell me if I did anything wrong? Thanks
 

gneill

Mentor
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Consider the trajectory of the jump: It's not a one-dimensional linear motion but rather a 2D curve, one with both horizontal and vertical components. The kinematic equation that you've chosen applies to motion in one dimension and doesn't take into account splitting the given velocity into components.

What's the optimum launch angle to maximize the range of a projectile? Have you covered the Range Equation in your classes? (If not you might want to look it up and try to remember it; it can really come in handy to avoid re-deriving the range of a projectile every time).
 

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