David kicks a soccer ball off the ground and in the air, with an initial velocity of 35 feet per second. Using the formula H(t) = -16t2 + vt + s, what is the maximum height the soccer ball reaches?

17.9 feet
18.2 feet
18.7 feet
19.1 feet
@amistre64 @triciaal @confluxepic

Question

David kicks a soccer ball off the ground and in the air, with an initial velocity of 35 feet per second. Using the formula H(t) = -16t2 + vt + s, what is the maximum height the soccer ball reaches? 

 17.9 feet
 18.2 feet
 18.7 feet
 19.1 feet
@amistre64 @triciaal @confluxepic

welshfella · Answer

i dont think there's enough information given to answer this question

anonymous · Answer

well thats all the info i got.

welshfella · Answer

we dont know the time t , we know  v and as the ball is on the ground we can take s  to be 0

anonymous · Answer

okay.

welshfella · Answer

so we have 

h(t) = -16t^2 + 35t

- 2 unknowns

anonymous · Answer

okay.

welshfella · Answer

oh if we differentiate we get

d h / dt = -32t + 35

and this = 0 for maximum h

so t =  35/32 seconds

and this gives h as  - 16 * (35/32)^2  + 35 *  35/32

anonymous · Answer

okay but im confused what do i do?

welshfella · Answer

hold on - have you done any  calculus  Finding derivatives?

anonymous · Answer

no

welshfella · Answer

oh ok

welshfella · Answer

well you can't do it that way then

anonymous · Answer

ohh

welshfella · Answer

we need to find the vertex of the graph -=16t^2 + 35t

the graph looks something like this

anonymous · Answer

i can graph it

welshfella · Answer

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