A 1200 kg car traveling initially with 25 m/s crashes into the rear end of a 480

Question

A 1200 kg car traveling initially with 25 m/s crashes into the rear end of a 4800 kg truck moving initially at 15 m/s in the same direction. Right after impact, the cars velocity drops to 11.0 m/s.
A.) what is the velocity of the truck just after the impact? How do you know?

B.) calculation the initial and final K.E. Of the individual cars, and hence, those of the total solutions?

C.) in the collision totally elastic? Is it completely inelastic? How do you know? Calculate the fractional loss of K.E. of the car-truck system. A 1200 kg car traveling initially with 25 m/s crashes into the rear end of a 4800 kg truck moving initially at 15 m/s in the same direction. Right after impact, the cars velocity drops to 11.0 m/s.
A.) what is the velocity of the truck just after the impact? How do you know?

B.) calculation the initial and final K.E. Of the individual cars, and hence, those of the total solutions?

C.) in the collision totally elastic? Is it completely inelastic? How do you know? Calculate the fractional loss of K.E. of the car-truck system.
A.) what is the velocity of the truck just after the impact? How do you know?

B.) calculation the initial and final K.E. Of the individual cars, and hence, those of the total solutions?

C.) in the collision totally elastic? Is it completely inelastic? How do you know? Calculate the fractional loss of K.E. of the car-truck system.

Explanation / Answer

m1 =1200 kg , m2 = 4800 m/s, u1 =25 m/s, u2 =15 m/s, v1 =11 m/s

(A) From conservation of momentum we can get truck velocity just after impact.

m1u1+m2u2 =m1v1+m2v2

(1200*25)+(4800*15) = (1200*11)+(4800*v2)

v2 =18.5 m/s

(B) K i = (1/2)m1u1^2 +(1/2)m2u2^2

= (0.5*1200*25*25) +(0.5*4800*15*15)

Ki =915000 J

(C) Kf = (1/2)m1v1^2 +(1/2)m2v2^2

= (0.5*1200*11*11) +(0.5*4800*18.5*18.5)

Kf =894000 J

Inelastic collision, If kinetic energy is conserved, then it is totally elastic collision. In this situation

Ki not equal to Kf. So it is inelastic collision.

Fractional loss of K.E = Kf/Ki = 894000)/915000

Fractional loss of K.E = 0.977

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