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this is one of many sample problems i have for homework and i dont understand them at all, can someone tell me how to do it so i can atleast try the rest? We have a test on this friday and i would like to know what im doing. thankss

  1. A speeder driving down the road at a constant 20 m/s, passes a patrolman parked roadside. The patrolman waits 3 secs, then pursues the speeder accelerating at a constant 4.0m/s(squared).

a. How long does it take for the patrolman to catch the speeder?

b. How far has he traveled before doing so?

Answers (2)

aa1ayyrzaa profile image
n1s2dgxnaa profile image

speeder is initially 3 sec ahead - at 20 m/s this is a distance = (3)(20) = 60 m

in order to gain 60 m on the constant velocity speeder, the patrolman in the

SAME time = t must travel:

60 + 20t = 1/2at² {where a = 4.0}

60 + 20t = (0.5)(4.0)t²

0 = 2.0t² - 20t - 60

solve for positive root of t:

t = 12.4 s ANS

substitute t into either (60 + 20t) or (1/2at²) to find ans for b.