## Jinnie 3 years ago A girl standing on the top of a building 200 feet highs throws a water balloon up in the air at a velocity of 30ft/sec. The equation for the height of the water balloon is h(t)=-16t^2 +30t + 200 Find the average velocity of the water balloon between 2 sec and 2.01 sec

1. shaan_iitk

abg velocity would be (h(2) - h(2.01))/(2-2.01)

2. Jinnie

how do i find the instantaneous velocity at two seconds and the direction of the water balloon

3. EdgeOfTheEarth

it involves calculus. do you know what a derivative is?

4. shaan_iitk

instantaneous vel would be dh/dt (differential wrt t) ...

5. shaan_iitk

direction of baloon would be the sign of the instantaneous velocity ..if it is positive then it would be in positive direction of the axis you are measuring your height anf vice versa

6. Jinnie

alright let me enter this into my calc and see

7. Jinnie

stay with me please. i need to know this question

8. Jinnie

am i plugging 2 into t^2 and 2.01 into 30t

9. shaan_iitk

no mate you plugging both into the h(t) function ... its like you finding the value of h(t) at 2 and again value of h(t) at 2.01 what class are you in?

10. Jinnie

calc

11. Jinnie

ok i see

12. shaan_iitk

with calc edgeoftheearth meant means calculus .. not calculator.. :)

13. Jinnie

i dont get you

14. shaan_iitk

do you have exposure in calculus?

15. Jinnie

am i familiar with calculus?

16. EdgeOfTheEarth

17. Jinnie

when i plug in 2, i get 196.3 and 2.01, I get 195.6584

18. EdgeOfTheEarth

does that make sense? you are basically finding the change in height (ft) from 2 to 2.01 seconds, and then dividing that by the change in time, .01 s

19. Jinnie

ok so i subtract 195.6584 from 196.3 and then divide by .01?

20. EdgeOfTheEarth

Yes, but your change in height is a little off.. h(2.01) = 195.6584 and h(2) = 196. 195.6584 - 196 = -0.3416.

21. Jinnie

i see

22. Jinnie

so for the instantaneous velocity, what must i do? i didnt understand you last time

23. EdgeOfTheEarth

for instantaneous velocity you have to take the derivative of the position function (h(t)).

24. Jinnie

i got zero, am i right?