Question

Help D: An object is dropped from a small plane. As the object falls, its distance, d, above the ground after t seconds, is given by the formula d = –16t2 + 1,000. Which inequality can be used to find the interval of time taken by the object to reach the height greater than 300 feet above the ground?

A.-16t^2+1000<300

B. -16t^2+1000<_ 300

C. -16t^2+1000>_300

D.-16t^2+1000>300

Answer 1

D.
`-16t^2+1000>300` is the correct answer.

Explanation:

It is given that Distance, d above ground with time 't' is given by the formula:

`d = -16t^2+1000`

The negative sign with
`16t^2` indicates that the distance is decreasing with square of time. i.e. value is getting subtracted from a value 1000.

For example, if t = 0, d = 1000 feet

If t = 2, d = -16
`*` 4 + 1000 = 936 feet

We can clearly see that when 't' is increasing, the distance 'd' is decreasing.

And at a certain time, the object will be on ground when d = 0 feet.

Inequality for the distance greater than 300 feet i.e.

d > 300 feet

Hence, the inequality will be:

`-16t^2+1000 >300` is the correct answer.