Question 1012435
During World War 1, mortars were fired from trenches 3 feet down. the mortars had a velocity of 150ft/s use the formula h=-16^2+vt+s to determine how long it will take for the mortar shell to strike its target?
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You didn't give an angle.  Are they firing straight up?  They'll be disappointed with the results.
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h=-16^2+vt+s
It's h=-16t^2 + vt + s --- not 16^2
h = -16t^2 + 150t - 3
Solve for t when h = -3, or when h = 0.
For h = 0:
h = -16t^2 + 150t - 3 = 0
*[invoke solve_quadratic_equation -16,150,-3]
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The small value is ground level ascending.
t =~ 9.355 seconds to impact at ground level.