If a ball is thrown vertically upward from the roof of a 48 foot tall building with a velocity of 80 ft/sec, its height in feet after t seconds is s(t)=48+80t−16t2
What is the velocity of the ball when it hits the ground (height 0)?

Question

If a ball is thrown vertically upward from the roof of a 48 foot tall building with a velocity of 80 ft/sec, its height in feet after t seconds is s(t)=48+80t−16t2
What is the velocity of the ball when it hits the ground (height 0)?

anonymous · Answer

Do you know derivative?

anonymous · Answer

yes

anonymous · Answer

@Chlorophyll can you help me out?

anonymous · Answer

i really hate word problems

anonymous · Answer

80-32 t

anonymous · Answer

You need to learn writing in equation:
v = - 32t + 80
From the height = 0, <=> s(t) = ...... = 0 => t = ...?
Then plug this t value into v!

anonymous · Answer

what do you mean <=>?

anonymous · Answer

Height            = 0
-16t² + 80t + 48 = 0

anonymous · Answer

ah ok got it thanks

anonymous · Answer

im sorry can be a little slow at times :P

anonymous · Answer

I'm trying to show you how to grasp the concept, so you'll able to be confident for testing time :)

anonymous · Answer

lol midterm was today and i forgot my calculator. didnt go very well :(

anonymous · Answer

because professor is a wingspan and wouldnt let me

anonymous · Answer

he isnt nice

anonymous · Answer

ya dont have a graphing calc yet so dont need batteries, and always have it with me but left it in my room because i fell asleep while doing my hw yesterday

anonymous · Answer

what grade are you in?

anonymous · Answer

sorry but can you help me set this up?
The radius of a spherical balloon is increasing at a rate of 2 centimeters per minute. How fast is the volume changing when the radius is 10 centimeters? 
Note: The volume of a sphere is given by V=(4/3)πr^3. 
i know what to do just not how to do it

anonymous · Answer

oh

anonymous · Answer

V  =   (4/3) π r³
->  v'  =    4 π r² r'
When r' = 2cm/ min, r = 10 cm,
=> v'  = 4 * 100 * (+2) = ....

anonymous · Answer

I meant :
=> v' = 4 * 100 * (+2) π  = ....

anonymous · Answer

402pi?

anonymous · Answer

oh nvm 800pi

anonymous · Answer

ya just added the 2 instead of multiplying it

anonymous · Answer

the next question could i try going through it step by step with you to make sure i have it?

anonymous · Answer

No, multiply with ( positive 2 since the rate Increasing)
-> v' = 4 π r² r'
=> v' = 4 * 100 * (+2) π

anonymous · Answer

Okie, but open the new post, though!

anonymous · Answer

is it just me or is this site really glitchie?

anonymous · Answer

No, that's the OS site bug!
My screen sometime jumping sometime froze out of control :(

anonymous · Answer

ya ok brb