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If an average-sized man with a parachute jumps from an airplane, he will fall 12.5(0.2t − 1) + 19t feet in t seconds. How long will it take him to fall 142 feet? (Round your answer to two decimal places.)

2 Answers

3 votes
Hi. Is the (.2t-1) supposed to be squared anywhere due to acceleration being rated with respect to time squared...? If not, all you have to do is create an equation:

142=12.5(.2t-1)+19t

Then, you factor out all those parts within the parenthesis to that 12.5, giving you:


142=2.5t-12.5+19t=21.5t-12.5

Move all non-t values to the numerical side:


142+12.5=21.5t

divide both sides by the coefficient of the variable t, and that will be your time, 7.186
User Ashish Agrawal
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8.4k points
6 votes

Answer:

It will take
7.19s to fall
142ft

Explanation:

We have the data of the function that represents the falling. Let's call this function ''f''. The function ''f'' depends of the time variable ''t''. We can write the function as :


f(t)=12.5(0.2t-1)+19t

In the function, if we replace the variable ''t'' by any value in seconds it will return the value in feets of how much the average-sized man has fallen for that value of ''t''.

In order to find how long it will take him to fall
142ft, we need to replace
f(t) by 142 and find the value of ''t'' that satisfies the equation.

Working with the function :


142=12.5(0.2t-1)+19t


142=2.5t-12.5+19t


154.5=21.5t


t=(154.5)/(21.5)


t=7.1860
7.19s

We can't forget in the last step that the unit for time in the function is seconds.

The correct answer is
7.19s

User Morten Holmgaard
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8.3k points