A ball is thrown vertically upward from a window that is 3.6mabove the ground. I

Question

A ball is thrown vertically upward from a window that is 3.6mabove the ground. Its initial speed is 2.8m/s.

a) With what speed does the ball hit the ground?
b) How long after the first ball is thrown should a second ball besimply dropped from the same window so that both balls hit theground at the same time?
Please show your steps, thanks! :) A ball is thrown vertically upward from a window that is 3.6mabove the ground. Its initial speed is 2.8m/s.

a) With what speed does the ball hit the ground?
b) How long after the first ball is thrown should a second ball besimply dropped from the same window so that both balls hit theground at the same time?
Please show your steps, thanks! :)

Explanation / Answer

A) you know acceleration equals -9.8 m/s. You also know thatwhen the ball comes back to the point that it is thrown from itwill have the same speed just in the opposite direction(downward). vi = -2.8 vf = -2.8 a = -9.8 d = 3.6 t = N/A so then use the equation: vf^2 = vi^2 + .5d solve for vf... NOTE: your answer is needs to be negative toaccount for the downward motion. b) I lied for this part the first time sorry: the correct way to do this is to calculate the time it takes forthe ball simply dropped to reach the ground so: vi = 0 vf = N/A a = -9.8 d = 3.6 t = ? vf = vi + at solve for t.. I'll now call it t(dropped) now we need to find the time it takes for the ball thrown to hitthe ground. but we have to do it in two steps. First the time till the top of it's motion: vi = 2.8 vf = 0 a = -9.8 d = N/A t = ? Use: vf = vi + at solve for t... now called t(thrown1) do the same thing again but this time for the ball falling from thetop of it's motion... we know the final velocity from above.. vi = 0 vf = (vf from part a) a = -9.8 d = N/A t = ? use: vf = vi +at solve for t.. now called t(thrown2) now: t(thrown1)+t(thrown2) = t(thrown total) t(thrown total) - t(dropped) = the time at which the 2nd ballshould be dropped. sorry for my mistake

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