A 5.0 kg block with a speed of 2.9 m/s collides with a 10 kg block that has a sp

Question

A 5.0 kg block with a speed of 2.9 m/s collides with a 10 kg block that has a speed of 1.9 m/s in the same direction. After the collision, the 10 kg block is observed to be traveling in the original direction with a speed of 2.4 m/s.
(a) What is the velocity of the 5.0 kg block immediately after the collision?
m/s

(b) By how much does the total kinetic energy of the system of two blocks change because of the collision?
J

(c) Suppose, instead, that the 10 kg block ends up with a speed of 3.8 m/s. What then is the change in the total kinetic energy?
J

Explanation / Answer

m1u1+m2u2=m1v1+m2v2 5*2.9+10*1.9=5*v+10*2.4 5v=9.5 v=1.9m/s velocity of 5lg block=1.9m/s total change in kinetic energy=1/2*5*(2.9^2-1.9^2)+ 1/2*10*(1.9^2-2.4^2) =12-10.75=1.25J if v2=3.8m/s m1u1+m2u2=m1v1+m2v2 5*2.9+10*1.9=5*v+10*3.8 5v=-4.5 v=-0.9m/s velocity of 5Kg block=-0.9m/s[opposite to initial direction] total change in kinetic energy=1/2*5*(2.9^2-(-0.9)^2)+ 1/2*10*(1.9^2-3.8^2) =38-54.15=-16.15J which is impossible,so this case wont exists.

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