## anonymous one year ago Okay, I have no clue what I am doing wrong. I've been following part a of this http://www.webassign.net/latex2pdf/2a2176c1f300dcc09b8a130c84af8595.pdf solution to help me with part a of this question I'm stuck on: If a rock is thrown upward on the planet Mars with a velocity of 18 m/s, its height (in meters) after t seconds is given by H = 18t − 1.86t^2. Find the velocity of the rock after two seconds. No matter what I do, it's still the wrong answer and it's becoming really frustrating considering that notes that my professor gave my class doesn't help with this at all.

1. Plasmataco

...

2. Plasmataco

im sry. only 13. I can try u know, being asian and all but no garentees.

3. Plasmataco

maybe just sub in 2 for t

4. Plasmataco

did u include direction? velocity is direction and speed.

5. Plasmataco

28.56 m/s upward?

6. anonymous

There's no direction at all. it has to be found the same way as the answer was found is the solution pdf I posted. This question has to be found the same was as that of solution a.

7. Plasmataco

.

8. Plasmataco

perhaps set ur limit to 2?

9. Plasmataco

I think u need to use derivative.

10. Plasmataco

try 10.56. if correct, i'll tell u why.

11. Plasmataco

hello?

12. anonymous

you have to find v(2)

13. Plasmataco

did she just leave?

14. Plasmataco

i think she just ditched which means eiither I got it right... or I MESSED UP AND SHE MAD.

15. anonymous

I left because you weren't helping me at all with what you were suggesting and was adding to my frustration. And surjithayer, I knew I had to find v(2), that's the whole point of the question but I was struggling with trying to get the correct answer.

16. anonymous

$\frac{ dH }{ dt }=18-2*1.8t=18-3.6t$ when t=2 v=18-3.6*2=18-7.2=10.8 m/s

17. anonymous

it is not 1.8 ,it is 1.86 2*1.86=3.72 when t=2 v=18-3.72*2=18-7.44=10.56m/s