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)
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Thread: Reps for physics help
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12-07-2010, 03:44 PM #1
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Reps for physics help
***SCC***
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12-07-2010, 03:50 PM #2
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12-07-2010, 03:57 PM #3
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Physics makes me hate school.Arnolds Six Rules of Success
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12-07-2010, 03:59 PM #4
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12-07-2010, 04:01 PM #5
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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.***SCC***
The gods will do nothing for us that we cannot do for ourselves.
"We are what we repeatedly do. Excellence, then, is not an act, but a habit." Aristotle
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12-07-2010, 04:06 PM #6
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12-07-2010, 04:13 PM #7
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Sort of. According to http://www.mcasco.com/qa_icel.html
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.***SCC***
The gods will do nothing for us that we cannot do for ourselves.
"We are what we repeatedly do. Excellence, then, is not an act, but a habit." Aristotle
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12-07-2010, 04:15 PM #8
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12-07-2010, 04:23 PM #9
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12-07-2010, 04:25 PM #10
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12-07-2010, 04:28 PM #11
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12-07-2010, 04:29 PM #12
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12-07-2010, 04:31 PM #13
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