Question

15 Ellen is at a hydroplane boat show. Starting from 1.0 miles away, the boat drives towards her and then passes her. The boat passes at a constant rate of 70 miles per hour. Ellen is given by d=l1.0-70tl. At what time is the boat 0.15 miles from Ellen? Calculate your answer in seconds.

Answer 1

D = d + Vt,
d = 1.0 miles,
V = -70 miles per hour,(- because its coming towards you)
And about D
Imagine you're standing at the centre of the street. a car is coming towards you. You can easily see that car will be X miles away from you two times. When Driving towards you And When Driving away from you. So
we have two D. + 0.15 miles and -0.15 miles.
0.15= 1 - 70t
-0.15=1-70t
From here
t equals
either
0.85/70 hours which is 0.85/70*3600 second about 43.7 sec.
or
1.15/70 hours or 1.15*3600/70 about 59 sec.