Hi, I need help on a physics question, so I decided to turn to you guys, lol.
anyways,
"A rock is thrown downward from the top of a 40 meter tower with an initial speed of 12 m/s. What is the speed of the rock just before hitting the ground?"
Speed of acceleration is 9.8m/s/s, of course. This isn't my question, by the way, as my school starts in 5 days. This is for my friend who lives in the US. I tried using 40 = 12m/s * t + 1/2(10)t^2 as an equation to find the time, then for the actual answer, i used x = vt + 1/2at^2.
When I went through all the steps to isolate t from the first equation, I got t=3.66~ which means v=48.66~ as a final answer. The only thing is, though, that it's multiple choice, and the answers are
a) 28 m/s
b) 30 m/s
c) 56 m/s
d) 784 m/s
right now, I think it's just 56m/s because it's the closest, but does anyone know the answer, and possibly, what i did wrong?





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