Question

Will rate response if answer is correct

For this question, itrs trying to find the relative speed of collision...

You're an investigator for the National Transportation Safety Board, examining a subway accident in which a train going at 84 km/h collided with a slower train traveling in the same direction at 21 km/h . Your job is to determine the relative speed of the collision, to help establish new crash standards. The faster train's "black box" shows that it began negatively accelerating at 1.9 m/s2 when it was 44 m from the slower train, while the slower train continued at constant speed.

What do you report?

Express your answer to two significant figures and include the appropriate units.

Answer 1

Initial velocity of falt train V_fo = 84 km/h = 84 times 1000/3600 V_fo = 23.33 m/s Initial Velocity of row train Vso = 21 km/h V_row = 5.83 m/s If are in the slow train looking of fact train coming towards us, our relative velocity is om/s and velocity or fast train coming towards us = 23.22 - 5.83 = 18.50 m/s new velocities Initial velocity of fact train = 17.5 m/s slow train = 0 m/s given x_f = 44 a_f = -1.9 m/s^2 V_f = aft + v_fa = -1.9t + 17.5 x_f = 1/2 at^2 + v_f0 t = 1/2 times -(1.9)t^2 + 17.5 t x_f = -0.95 t^2 + 17.5 t 44 = 0.95 t^2 + 17.5 t 0.95t^2 -17.5t + 44 = 0 t = -B plusminus squareroot B^2 + 4ac/29 = 17.5 plusminus squareroot (17.5)^2 -4(.95)44/2 times 0.95 = 17.5 plusminus 11.79/1.9 t = 3, 15.41 The relative eq. of speed is fact train t = -3 sec