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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?

vf^2= vi^2+2ax

Yeha boreas is right,
the answer is actually 30 m
Dunno what you did wrong, but I don't like solving quadratics in these physics questions lol, unless absolutely necessary

Don't forget to count for wind drag, terminal velocity, altitude, and any other weather oddities. (I pray your teacher isn't that picky)

There's not enough info for that, and this sounds like a normal highschool class, which probably doesn't get into that anyway. Plus at 40m there wouldn't but much chance for anything to make much of a difference.

If this is a school question you don't take into account those things.

They should at least observe some of the basic rules of physics- some of the word problems they give for quadratic equations are just ludicrous. I once had this one involving people parachuting from a plane and you had to figure out how long it would take them to reach a certain height- however if you calculated their speed based on their rate of descent, you would find that they rapidly accelerated to upwards of 600mph and would have become human torches and burnt up in the atmosphere.

ya we just started doing velocity and stuff at school. its pretty ez just follow the equations. that u r given. if u have one

From: RiotMaker75
ya we just started doing velocity and stuff at school. its pretty ez just follow the equations. that u r given. if u have one

Useless poster. Don't spam.