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A ball with a mass of #15 kg# moving at #15 m/s# hits a still ball with a mass of #17 kg#. If the first ball stops moving, how fast is the second ball moving? How much kinetic energy was lost as heat in the collision?

Answer 1

well as no external force is acting during this motion and collision,we can say,the linear momentum of the system will be conserved.

So,let the 2nd ball will move with a velocity of #v# after the collision.

So,momentum before the collision is #(15*15 +17*0) Kgms^-1# (considering the #2# nd ball was at rest before the collision)

And,momentum after the collision will be #(15*0 + 17*v) Kgms^-1#

So,we can equate both,

#15*15 = 17*v#

So, #v=13.234 ms^-1#

so,initial kinetic energy of the system was, #K.E _(i)=1/2 15 *15^2 J#(using, #K.E. =1/2 mv^2#)

And,after the collsion it became #K.E_(f)=1/2 17 (13.234)^2 J#

So,energy lost is #K.E_(f) - K.E(i) =198.81 J#

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Answer 2

Charles Aeschliman

The second ball will move at 13 m/s. The kinetic energy lost as heat in the collision is 825 J.

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Answer from HIX Tutor

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.