Word problem

Question

A stone dropped from the rest travels 387 feet in the first 7 seconds. How far will it have fallen at the end of 8 seconds?

Answer 1

s = (1/2)*a*t^2

 

387 feet in 7 seconds  ==>  

 

387 = (1/2)*a*7^2

a = 15.7959 ft/sec^2 

 

s(8) = (1/2)*15.7959*8^2 = 505.47 feet 

 

Since s varies directly with the square of t you could also get this result by multiplying 387 by the square of the ratio of the two times 

 

s(8) = 387*(8/7)^2 = 505.47 feet