Question

Question! Okay, I don't know if this is just frustrating me or I'm just making it harder. So: A rock is dropped from a tree of height 28 m into a lake (depth 4.0 m) below. After entering the water, the rock floats gently down through the water at a constant speed of 1.6 m/s to the bottom of the lake. What is the total elapsed time?
Okay, so I took the time the rock was in the air and I got 2.56 seconds and then I took the time when the rock was in the water and that was 2.5 seconds. So of course I added them together and the answer was wrong.

Answer 1

is the answer 4.89s?

Answer 2

hang on let me see...

Answer 3

oh snap. Yes it is! May you tell me how you solved it?

Answer 4

Thank you very much, by the way. I really appreciate it.

Answer 5

I think I got how to solve for the time in the air, but i may have messed up on trying to calculate the time in the water.

Answer 6

actually you got it backwards
the one in the water is correct

Answer 7

please show me how you solved the air time

Answer 8

So i think what i did was used the equation of x=x0+v0t+1/2at^2 and since the height starts from the top of the tree, i used 28 as my initial and 0 as my final position.

Answer 9

then I just plugged in the values of the gravity and solved for time.

Answer 10

DId i choose the wrong equation?

Answer 11

that's actually correct; try doing that calculation again

Answer 12

you should get 2.39s

Answer 13

Oh wow....you know what, i added in the wrong value for the initial height..shoot...that's why I kept getting the wrong answer.

Answer 14

Thank you so much for your help. I"ll try to be more cautious of my algebra and values.

Answer 15

no prob; we help each other :)