Nelson O.

# Physics (momentum)

A rock is thrown vertically upward from ground level at time t =0. At t =1.5 s it passes the top of a tall tower, and 1.0 s later it reaches its maximum height.What is the height of the tower?

I was able to get the answer on my second try (when I calculated for the initial velocity at ground level when rock was thrown to final velocity of when it reaches max height; then using that answer to find out the height), however I want to understand why I was not able to get the answer (~26 meters) when I attempted to solve it in a different way:

I first made a line of A ---> B where A was ground level and B was where the rock reaches the height of the building at 1 second. I then made a second line connecting that B point to C where C is the max height of the rock thrown (Where V final is 0) at the 2.5 second mark. I then calculated B------>C to figure out the velocity at point B (with the assumption that that would work as the initial velocity for where B starts, and the final velocity for AB, where B is the same height as the building. I then calculated that Velocity and used it to find the height of the building, however I did not come to the same answer. Why was that?

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