Placing x-markers to drop water balloon on students

[negation]

Homework Statement

You and your roommate plot to drop water balloons on student entering your dorm. your window is 20m above the side walk. You plan is to place an x on the side walk to mark the spot a student must be when you drop the balloon. You note that most student approach the dorm at 2ms^-1. How far from the impact point do you place the x?

Homework Equations

None

The Attempt at a Solution

 

[voko]

The first half, where you computed the free falling time, is correct. The second half - where does 2 ms^-2 come from?

 

[negation]

The first half, where you computed the free falling time, is correct. The second half - where does 2 ms^-2 come from?

Opps. A slip in the label of unit which had me confuse velocity for acceleration. I'll redo it. Can I assume acceleration is 0ms^-2? I think I could since the walking velocity is constant, acceleration is zero.

 

[negation]

xf - xi = 2ms^-1 (2.0192751098s) + 0.5(0ms^-2)(2.019275109s)^2 = 4.03855m

 

[voko]

Good, but you have way too many "significant" figures.

 

[negation]

Good, but you have way too many "significant" figures.

rounded off to 4.03m