+72 A car blows past a trap going 162 km/h. A police car starts to move 5 seconds after the speeding car passes it, accelerating at 6 m/s^2. How long will it take the police car to catch the speeder?
Please provide explanations and full solutions!
Thanks, very much!
+37146 You are correct....that was in my correction.....but you may have posted before I corected it! Good call!
+72 If this helps, the answer is 30.4 seconds. However, I always get different solutions.
+37146 MT.....does the car keep accelarating until it catches the speedster in your answer?
+37146
CORRECTION: wrong units corrected below and added distance for 5 seconds
Speedster displacement= 162 k/hr x t Which equals 162 x 1000/=3600 m/s = 45 m/s 45 x t + (45 x 5) = displacement
Police car x= displacement = x0 + vo t + 1/2 at^2 (x0=0 vo t =0) and it has to equal 45 x t + 225
so
45t +225 = 1/2 at^2
90t +450 = at^2 and a=6
6t^2 - 90t-450=0
t^2 -15t-75=0
Quad formula 15+-sqrt(225+300) / 2 = 18.95 seconds
Hope i did that correctly!
EP: I don't know much about physics, but shouldn't the 5 seconds' delay by the police officer be taken into account in the sense that the speeder has already travelled: 5 x 45 =225 meters??.
+37146 You are correct....that was in my correction.....but you may have posted before I corected it! Good call!
