e Take a Test Antrell Bend Internet Explorer L httpsedge P h

e Take a Test Antrell Bend Internet Explorer L https://edge P http Student/Play Test d-122972105& yes bing Antrell Bender 2/18/16 3:02 Pl YAHOO Test Week 10: Test 5 Time Limit 02:30:00 Submit Test American University This Question 1 pt AMU 3 of 25 This Test: 25 pts possibl Home Announcements The stopping distance d of a car after the brakes are applied varies directly as the square of the speed r. If a car traveling 40 mph can stop in 70 ft, how many feet will it take the same car to stop when it is traveling 120 mph? Calendar It will take ft. Messages (Simplify your answer. Type an integer or a fraction.) Forums Syllabus Lessons Adobe Connect My Math Labs Resources Assignments Tests & Quizzes Gradebook 13 Help Roster Enter your answer in the answer box. Campus Save for Later Next Question Lounge APUS Library HE Search the web and Windows Tools (Alt+X) Logou 3:03 PM 2/18/2016

Solution

Given that stopping distance d varies directly as square of speed r

==> d r²

==> d = k r² ( k is proportionality constant)

r = 40 mph ==> d = 70 ft

==> 70 = k (40)²

==> k = 70/(40)²

==> k = 7/160

==> d = (7/160) r²

==> d = 7r²/160

when r = 120 mph

==> d = 7(120)²/160

==> d = 630 ft

Hence the car travelling at 120 mph comes to stop in 630 feet