0
$\begingroup$

I am given that a bullet of mass 24.6 grams is shot at a block of 231 grams that will slide on a wooden desk with a coefficient of kinetic friction being .210. all i'm given is that the block more 32.6 meters. The problem is asking for the initial velocity of the bullet.

I know this has something to do with conservation of momentum but I can't find the Final velocity of the system especially without an applied force or some time.

$\endgroup$
  • $\begingroup$ When you say 32.6 meters, is that the stopping distance of the bullet plus block after the collision? $\endgroup$ – Bob D Dec 7 '19 at 18:53
  • $\begingroup$ Yes that is the stopping distance of the bullet plus the Block $\endgroup$ – Hector Espinoza Dec 7 '19 at 18:55
  • $\begingroup$ Hi and welcome to physics.SE! Please note that homework-like questions and check-my-work questions are generally considered off-topic here. We intend our questions to be potentially useful to a broader set of users than just the one asking, and prefer conceptual questions over those just asking for a specific computation. $\endgroup$ – ACuriousMind Dec 7 '19 at 19:29
0
$\begingroup$

Hint: (1) Use conservation of momentum to get the initial velocity of the bullet+block as a function of the initial velocity of the bullet, (2) use the work energy theorem to obtain the initial velocity of the bullet+block immediately after impact based on the friction work needed to bring it to a stop.

Hope this helps.

$\endgroup$
  • $\begingroup$ For the first hint, I should solve the conservation of momentum equation for the term of initial velocity of the bullet. For the second hint, I'm still not able to find how to incorporate the force of friction into the problem. thank you for the help anyway. $\endgroup$ – Hector Espinoza Dec 7 '19 at 19:11
  • $\begingroup$ The first hint gives you an equation with two unknowns, the initial velocity of the bullet and the initial velocity of the bullet+block. The second hint allows you to calculate the initial velocity of the bullet+block just after impact. Do you know how to calculate the friction force? Do you know the work energy theorem? $\endgroup$ – Bob D Dec 7 '19 at 19:17
  • $\begingroup$ We can only give guidance on these types of questions, not complete solutions, per the policy of this site for homework and exercise type questions. You need to know the work energy theorem and how to calculate the friction force and friction work. If you don't know these, you need to research them. $\endgroup$ – Bob D Dec 7 '19 at 19:20
  • $\begingroup$ I understand thank you for the help, I believe I have it from here. $\endgroup$ – Hector Espinoza Dec 7 '19 at 19:26
  • $\begingroup$ Good, glad to help $\endgroup$ – Bob D Dec 7 '19 at 19:27

Not the answer you're looking for? Browse other questions tagged or ask your own question.