Q9. A bullet of mass m is fired horizontally with speed vi at a wooden block of

Question

Q9. A bullet of mass m is fired horizontally with speed vi at a wooden block of mass mw resting on a frictionless table. The bullet hits the block and becomes completely embedded within it. After the bullet has come to rest within the block, the block, with the bullet in it, is traveling at speed w. Before collision After collision (a) [4 pts] Which of the following quantities, if any, are conserved during this collision? [A] kinetic energy only [B] momentum only [C] kinetic energy and momentum [D] neither momentum nor kinetic energy (b) [4 pts] Which of the following best describes this collision? [A] perfectly (completely) elastic c perteaty coampictely) inelsic

Explanation / Answer

(a) Before the collision the bullet has speed but the wooden block is at rest. After the collision bullet has no speed but the total system has.
So the bullet lost it's kinetic energy and transferred it to the block.
Clearly, kinetic energy is not conserved here.
Momentum is always a conserved quantity as long as there is no friction.
So correct option is [B].

(b) Since kinetic energy and momentum is not conserved it not a perfectly elastic collision.
As the total system is not losing energy it is not partially inelastic collision also.
So correct option is [B].

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