A 1 275.0 kg car traveling initially with a speed of 25.000 m/s in an easterly d

Question

A 1 275.0 kg car traveling initially with a speed of 25.000 m/s in an easterly direction crashes into the back of a 8 300.0 kg truck moving in the same direction at 20.000 m/s. The velocity of the car right after the collision is 18.000 m/s to the east.

(a) What is the velocity of the truck right after the collision? (Give your answer to five significant figures.)
  m/s east
21.07
(b) What is the change in mechanical energy of the car

A 1 275.0 kg car traveling initially with a speed of 25.000 m/s in an easterly direction crashes into the back of a 8 300.0 kg truck moving in the same direction at 20.000 m/s. The velocity of the car right after the collision is 18.000 m/s to the east. (a) What is the velocity of the truck right after the collision? (Give your answer to five significant figures.) m/s east 21.07 (b) What is the change in mechanical energy of the car?truck system in the collision? -9516.165 Your response differs from the correct answer by more than 10%. Double check your calculations. J

Explanation / Answer

Conservation of momentum

1275 . 25 + 8300 . 20 = 1275 . 18 + 8300 . V

197875 = 22950 + 8300 V

V = 174925 / 8700 = 21.07 m/s ( speed of truck after collision )

b) energy before = 0.5 . 1275 . 25^2 + 0.5 . 8300 . 18^2 = 1743037.5 J   

energy after = 0.5 . 1275 . 18^2 + 0.5 . 8300 . 21.07^2 = J 206550

Energy lost = 417706 J

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