physic
posted by aisya .
a bullet is fired from the ground at the angle of 30 degree above the horizontal,What initial speed must the bullet have in order to hit a point 250 ft high on a tower located 400 ft away (ignoring air resistance),what the solution?

Write vertical and horizontal equations of motion. Require that X = 400 and Y = 250 at same time, t. You have two equations for the two unknowns, t and Vo. They are:
X = Vo*cos30 * t = 400
Y = Vo*sin30 * t  (g/2) t^2 = 250
I recommend using the X equation to substitute for t in the second (Y) equation.
g = 32.2 ft/s^2.