Projectile with different landing height

[bionut]

Homework Statement

A handball is projected at an angle of 30 degrees with the horizontal from a 20 meter tower with an initial vertical velocity of 10 ms and an initial horizontal velocity of 20 ms. Find the total time of flight.

Homework Equations

The Attempt at a Solution

I know that 0=Vi + at will give me time up X2 will give total time for a projectile with same landing height, but what do I need to use if it has a different landing height?

 

[1MileCrash]

IIRC that's a lot more info than you need, you only need a function to describe the position of y at any given t, and solve for 0. Since they didn't give you a vector, but an explicit description of vertical velocity, this shouldn't be hard.

If your position is initially 20m, then

y = 20 +...

Your velocity is 10 m/s

y = 20 + 10t

Minus acceleration due to gravity..

y = 20 + 10t - 4.9t^2

Should describe your projectile at any t.