Finding velocity of lump of clay. (Not too sure on answer)

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Homework Statement


Two lumps of clay, each with the same mass 3.5 kg, are sliding on ice, with no friction. One is moving at 4.8 m/s to the right, the other is moving at 2.3 m/s to the left. They collide and stick to one another. Calculate the velocity of the lump of clay after the collision. Is the total kinetic energy constant?

Homework Equations


(m1+m2)vf=m1v1+m2v2

The Attempt at a Solution


Substituted m1 and m2=3.5 kg, v1=-2.3 m/s, and v2=4.8 m/s. With that, I got vf=1.25 m/s. I'm almost sure that one of the velocity is negative since one lump of clay is moving in the opposite direction away from the other. For the second question of whether or not total kinetic energy is constant, I said no.
 

Answers and Replies

  • #2
ehild
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Homework Statement


Two lumps of clay, each with the same mass 3.5 kg, are sliding on ice, with no friction. One is moving at 4.8 m/s to the right, the other is moving at 2.3 m/s to the left. They collide and stick to one another. Calculate the velocity of the lump of clay after the collision. Is the total kinetic energy constant?

Homework Equations


(m1+m2)vf=m1v1+m2v2

The Attempt at a Solution


Substituted m1 and m2=3.5 kg, v1=-2.3 m/s, and v2=4.8 m/s. With that, I got vf=1.25 m/s. I'm almost sure that one of the velocity is negative since one lump of clay is moving in the opposite direction away from the other. For the second question of whether or not total kinetic energy is constant, I said no.
The final speed is correct, but you should state, what is the direction of it.
Yes, the kinetic energy is not conserved, but you should show its numerical value. Did it increased or decreased with respect to the initial one?
 

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