People also like to think that kinetic energy is conserved during this collision. Most people are willing to accept that momentum is conserved (although if you consider the block rising with the gravitational force, momentum ISN'T conserved). Here is the main problem with this question. Both blocks will have the same speed after the collision with the bullet.Д«UT WAIT! What about the spinning? Doesn't that take extra energy? Well, there is certainly energy associated with the spinning of the block (we call this rotational kinetic energy). So the momentum of the bullet and block must be the same no matter where the bullet hit the block. Where in the derivation above does it indicate if the bullet hit the center or side of the block? It doesn't. Since the bullet pushes on the block the same as the block pushes on the bullet, the changes in momentum for the bullet and block are (I will use the subscript b for the bullet and w for the wooden block): Second, the momentum principle says that this force changes the momentum of the object. First, the bullet exerts a force on the block AND the block pushes back on the bullet with the same magnitude of force (it's the same force) for the same time. In a simple collision like this, there are two important ideas. A bullet is then shot horizontally into the two blocks so that they slide across the ice at the same speed.

Instead, let me consider two blocks sitting on frictionless ice. This means that I don't really need to worry about the 'rising' part of the video. The two blocks rise to the same height because they start with the same initial translational velocity. Why do the two blocks go the same height? First, let me change the problem a little bit. However, I think I can do a better job here in a blog post. I have a slightly more detailed answer in a video if you like. The non-spinning block only has gravitational potential energy - so shouldn't it go higher? My simple answer: But why? Why do the two blocks go the same height? If you look at energy, the spinning block has gravitational potential energy as well as spinning energy. Even after you see the answer, you still want more. It's not just me - there was lots of internet-based discussion on this particular problem.ДЄnd here is where you can see that this is an epic question. I think that obsession is the key to a good problem.

Finally, this is a nice problem because it makes me obsessed.

If it made you happy, you could even do a video analysis of the block.

Of course the video question makes it a little more compelling because it's real. Actually, this is essentially a problem straight from my favorite introductory textbook - Matter and Interactions.

You could approach this problem from a very conceptual level or use more sophisticated physics.

I mean, he's smarter every day, right? I'm not saying the smart-levelness increases linearly, but smarter is smarter. Just a note - Destin has to be a smart guy. The Veritasium video even shows that Destin (from Smarter Every Day) and Henry (M inute Physics) sure of the answer. Even experts aren't so sure of the answer.I think I could show this video to a 4th grade class and they would have an opinion about which will go higher. This isn't a question that only experts could guess at. Just about everyone can come up with a plausible answer.This isn't some hypothetical question in a book. They really did shoot a bullet into a block of wood to see it rise up. Here are some possible reasons why this is a great question. If you look at the Veritasium videos, you will find many experiments like this. But maybe you want to think about this problem, if so you can just read this next part and then come back later. Yes, of course I am going to go over the answer - mostly because I enjoy that. Really, I want you to think about it for a moment.

Create a bullet force 2 accaunt