An object is dropped from the top of a 100-m tower. its height above ground after t sec is 100-4.9t^2 m. How fast is it falling 2 sec after it is dropped?

Question

An object  is dropped from the top of a 100-m tower. its height above ground after t sec is 100-4.9t^2 m. How fast is it falling 2 sec after it is dropped?

anonymous · Answer

Well, the initial height here is 100, and the position equation you have is $$100-4.9t^2 $$ and the time given is t=2 seconds, so in this case you just substitute 2 in your equation for t and there's your answer.

anonymous · Answer

plug 2 in for t

anonymous · Answer

That only gives me the height above ground after 2 seconds. I need to know how fast it is falling at that point.

anonymous · Answer

Oh, I misread. Have you taken yet?

anonymous · Answer

taken calculus*

anonymous · Answer

That's what I'm working on now. In my book, the answer is 19.6 m/s, but I keep getting -19.6 m/s.

anonymous · Answer

Yeah when I work it out I also get -19.6 so either we're making the same mistake or the book has a typo. From a physics standpoint a negative velocity makes more sense to me because of the downward direction but I haven't taken either physics or calculus for a while so I might be rusty. Sorry

anonymous · Answer

No problem. Thanks for the help.

goformit100 · Answer

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