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**1. Homework Statement**

A projectile is launched over level ground on an unnamed planet. The equation of the projectile's vertical position is y(t)=-6t

^{2}+48t-90.

a. Determine the acceleration due to gravity on this planet

b. Determine (y

_{max}, t

_{ymax}), the coordinates of the maximum height of the projectile in the t-y plane

**2. Homework Equations**

r

_{f}=r

_{i}+v

_{i}t+1/2gt

^{2}

**3. The Attempt at a Solution**

I know r

_{i}=0 because that's the origin

Since I'm not given a time or velocity I'm stuck on how to solve for anything