Question

An object is dropped from a height of 1700 ft above the ground. The function h=-16t^2+1700 gives the object’s height h in feet during free fall at t seconds.
a. When will the object be at 1000ft above the ground?
b. When will the object be 940ft above the ground?
c. What are a reasonable domain and range for the function h?

Answer 1

both part a and b are asking you to find the time t for a given h.

for a, solve the following equations for t:
-16t^2 + 1700 = 1000

Answer 2

t=(close to) 1.654 is what I got a.

Answer 3

I got t = 6.614

-16t^2 +1700 = 1000
-16t^2 = -700
t^2 = 43.75
then take square root of both sides

Answer 4

1000=-16t^2+1700
-700=-16t^2
_/-700=_/-16t^2
26.458/16=16t/16
t=1.654
is what I did

Answer 5

You need to divide by 16 first, before you take the square root.

Answer 6

Okay got a. and b. now I just need c.:)

Answer 7

Domain = what values of time would be used here?
t > 0, since negative time not reasonable. And you probably need to find when the ball hits the ground, since after that time, the ball would be underground.

Answer 8

1700=16t^2
_/-106.25=t^2
t=10.3078
Is what I got for how long it takes to hit the ground.

Answer 9

Cool. So the a reasonable domain is from 0 to 10.3078.

Answer 10

Range: what values of height seem reasonable?
h > 0, because negative height would mean that the ball was underground.
And ... since the ball was "dropped" from a height of 1700 (vs being "thrown up" from a height) the maximum height would be 1700.
So ... a reasonable range would be from 0 to 1700.