Physics: Its one question and 2 parts please i just need right answeer. Collisio

Question

Physics:

Its one question and 2 parts please i just need right answeer.

Collisions

A block with a mass of m1 = 6.9 kg is pushed to the right with a force of 732 N for a distance of 3 m across a horizontal frictionless surface, after which the force is removed. The 6.9-kg block then collides with a second block with a mass m2= 2.9 kg, which is initially at rest. The two blocks stick together after the collision.

1) Determine the change in the internal energy of the system of blocks during the collision.

____________J

2) Now assume that the 2.9-kg block is traveling at 3.7 m/s to the left before the collision. The two blocks will still stick together after the collision. Determine the change in the internal energy of the system of blocks.

_____________J

Explanation / Answer

1) Work of m1 = 732*3 = 2196 J
Velocity of m1 = sqrt((2*2196)/6.9) = 25.23 m/s

6.9*25.23 = (6.9+2.9)*vfinal
=> vfinal = 17.76 m/s

KEfinal = 1/2(6.9+2.9)*17.76^2
= 1545.55

So,
KEchange = 2196 - 1545.55
= 650.45 J

2)
Vfinal = (6.9*25.23+2.9*3.7)/(6.9+2.9)
= 18.86 m/s

KEinitial of m2 = 1/2(2.9*3.7^2)
= 19.85 J

Initial KEtotal = 2196+19.85 =2215.85 J

KEfinal = 1/2(6.9+2.9)*18.86^2 = 1742.93 J

So,
KEchange = 2215.85 - 1742.93 = 472.9 J or 473 J

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