Cannon fired upward at 25 m/s reaches 50 m, finding g

[BTurner90]

Homework Statement

A cannon is fired on another planet straight up at 25 m/s. It reaches a maximum height of 50m. What is the value of the gravitational acceleration?

Homework Equations

v = v_i + at
x = .5 (v_i + vt)

The Attempt at a Solution

using the first equation,
a = (v - v_i)/t
a = (0-25)/2
g = -12.5 m/s^2
Where am I going wrong? Thanks

 

[tiny-tim]

Welcome to PF!

Hi BTurner90! Welcome to PF!

(try using the X² tag just above the Reply box )

A cannon is fired on another planet straight up at 25 m/s. It reaches a maximum height of 50m. What is the value of the gravitational acceleration?

There are three standard constant acceleration equations, so choose the one that only has what you already know, and what you want to know.

In this case, you don't have t, and nobody's asking you for it, so choose an equation with u v a and s.