Problem 5 A car, with an inertia of 1000kg, is stopped at a stop sign on an icy

Question

Problem 5 A car, with an inertia of 1000kg, is stopped at a stop sign on an icy intersection. A truck, with an inertia of four times that of the car, is unable to stop on the icy road and collides with the stopped car. The bumpers crumple, locking the vehicles together, and they slide off together into the intersection. If the initial velocity of the truck was 30% (a)Find the amount of kinetic energy that was converted to other forms in the collision from the reference frame of the Earth. b)What is the gain in the car's kinetic energy? (c)Why does the metal get hot?

Explanation / Answer

Applying momentum conservation for the collision,

(1000 x 0) + (4 x 1000 x 30) = (5 x 1000) v

v = 24 m/s

(A) Ki = (4000) (30^2) /2 = 18 x 10^5 J

Kf = (5000)(24^2) /2 = 14.4 x 10^5 J  

lost energy = Ki - Kf = 3.6 x 10^5 J  

(B ) Kgain = (1000)(24^2) /2 = 2.88 x 10^5 J

(C) because that lost kinertic energy convreted into heat energy.

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