Reps for physics help

Collision problem, and I can't figure out how they got this answer.


You have been asked to design a 'ballistic spring system' to measure the speed of bullets. A bullet of mass m1 is fired into a bullet of mass M2. The block, with the embedded bullet, then slides across a frictionless table and collides with a horizontal spring whose spring constant is k. The opposite end of the spring is anchored to a wall. The spring's maximum compression d is measured.

Find an expression for the bullet's speed VB in terms of m1, M2, k, and d.


The back of the book says

VB= sqrt((m1+m2)*kd^2)/m^2)

Lol I still can't pass optics

[img]http://files.sharenator.com/Whats_Going_On_In_This_Thread_Huge_Collection_of_Randoms-s400x541-66557.jpg[/img]

Physics makes me hate school.

sounds to me like you just have to plug in the numbers

[QUOTE=.Excalibur;589860303]sounds to me like you just have to plug in the numbers[/QUOTE]

No, it wants the general formula using variables. I figured it out though. Next question, which I just can't remember how to do, is how to find energy lost in a collision.

edit: The answer I gave at the bottom of the post is what the book said the answer was. I think I figured out why.

[QUOTE=Father of Cajun;589861603]No, it wants the general formula using variables. I figured it out though. Next question, which I just can't remember how to do, is how to find energy lost in a collision.

edit: The answer I gave at the bottom of the post is what the book said the answer was. I think I figured out why.[/QUOTE]

Energy lost in a collision?

As in measure the amount of energy the object had before impact?

[QUOTE=iJarhead;589863863]Energy lost in a collision?

As in measure the amount of energy the object had before impact?[/QUOTE]

Sort of. According to [url]http://www.mcasco.com/qa_icel.html[/url]

It's simply 1/2 m*v^2 of the objects before minus 1/2m*v^2 of the object after.

Given that the speed of the bullet is 200 m/s and the mass of the bullet is 5 g. the mass of the block it hits is 2 kg

1/2(.005 kg)(200m/s)^2=100 N


after impact, 1/2(2.005 kg)(.499 m/s)^2=.24N


never mind. That's the right answer<_<. Thanks guys.

[QUOTE=Father of Cajun;589853093]Collision problem, and I can't figure out how they got this answer.


You have been asked to design a 'ballistic spring system' to measure the speed of bullets. A bullet of mass m1 is fired into a bullet of mass M2. The block, with the embedded bullet, then slides across a frictionless table and collides with a horizontal spring whose spring constant is k. The opposite end of the spring is anchored to a wall. The spring's maximum compression d is measured.

Find an expression for the bullet's speed VB in terms of m1, M2, k, and d.


The back of the book says

VB= sqrt((m1+m2)*kd^2)/m^2)[/QUOTE]

if thats what college level looks like then i am phucked.

[QUOTE=MistuuhMitch;589868543]if thats what college level looks like then i am phucked.[/QUOTE]

Tbh, this is one of the easier ones, but I'm on Fluids and stuff now and I was just having a brainfart with this.

if you tell me what text book your using, chapter and problem, i can look it up

[QUOTE=AdamBombed;589874063]if you tell me what text book your using, chapter and problem, i can look it up[/QUOTE]

:O Physics: A Strategic Approach by Randall D. Knight,2nd edition.

I'll PM you with a problem in a minute. I figured that one out and I'm working through some more now.

"College Physics: A Strategic Approach (2nd) textbook problems explained step-by-step"

cramster ftw, pm away

[QUOTE=AdamBombed;589876413]"College Physics: A Strategic Approach (2nd) textbook problems explained step-by-step"

cramster ftw, pm away[/QUOTE]

Thanks man :D I will for sure, just let me find one I can't figure out.