A 1 125.0 kg car traveling initially with a speed of 25.000 m/s in an easterly d

Question

A 1 125.0 kg car traveling initially with a speed of 25.000 m/s in an easterly direction crashes into the back of a 8 900.0 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

(b) What is the change in mechanical energy of the car–truck system in the collision?

J

(c) Account for this change in mechanical energy.

Explanation / Answer

using momentum conservation for collision between two cars,

1125 x 25 +   8900x20   = 1125 x 18   + 8900v

v = 20.88 m/s after collision speed of truck.

b) initial energy = (1125 x 25^2 /2 ) + (8900 x 20^2 / 2)   = 2131562.5 J

final energy = (1125 x 18^2 /2 ) + ( 8900 x 20.88^2 / 2) = 2123234.02 J

change in energy = final energy - initial energy = - 8328.48 J

c) there is loss in mechanical enrgy .

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