The Bullet Block Experiment
Why Physics Stack Exchange recommends it
Physics Stack Exchange users link it as the standard reference example when questions come up about off-center impulses, rotation, and where the energy goes in inelastic collisions.
Recommended by 1 people across 2 different months, 2013 to 2024.
What it is
A short Veritasium demo in which a bullet is fired upward into a wooden block, once through the center and once off-center, and viewers are asked which block rises higher. It uses high-speed footage filmed with help from RIT and Dickinson College, and points to follow-up videos with the answer.
What people said
Recommends Farcher · 2016-08 · Physics Stack Exchange · on “Applying a force on an object in space (weightless) away from its centre of mass vs at its centre of mass”
I think that you query is about equating the work done by the accelerating force and the gain in kinetic energy of the bar. If the force $F$ is applied at the centre of mass of the bar and the centre of mass moves a distance $x$ then the work done by the force is $Fx$ and this represents the gain in the translational kinetic energy of the bar. If the same force is applied along a line which is not through the centre of mass of the rod and the centre of mass moves by a distance $x$ the work done by the force is larger than $Fx$ because, if the force is to stay in contact with the rod which is rotating about its centre of mass as well as the centre of mass undergoing transnational motion, the
Recommends Farcher · 2024-12 · Physics Stack Exchange · on “Why does a rod move faster when struck at the center rather than the edge, despite Newton's second law indicating the same acceleration?"”
One word explains why your ideal world analysis disagrees with your real world observation - friction. Ideal world analysis Linear acceleration of centre of mass of the rod is the same irrespective of where the rod is hit. Angular acceleration about centre of mass is greater when the applied force applies a larger torque about the centre of mass, ie force is applied at right angles to the rod and further from the centre of mass. Real world observation Contradicts theory, as explained above, because of the presence of friction and so much so that many think the theoretical analysis is flawed. In some ways this is like the old idea that a force needed to be applied to a cart (or any other obje
Cites Sourabh · 2013-08 · Physics Stack Exchange · on “Veritasium - Firing bullet in block - along center and away from center”
This question is about this video on YouTube [this video] , in which a bullet is fired vertically into the center of a wooden block from below, sending the block up into the air. Next, a bullet is fired vertically but off-center into a similar block from below, again causing the block to rise into the air, but simultaneously to rotate. The video asks for a prediction as to which block will rise higher. Please post your guess/prediction/solution along with answer or in comments. My first guess was that air friction decreases when object is rotating, but now I think that's not the reason. Someone please shed some light on this. EDIT Is it possible that the first bullet went deeper inside the first
Cites Juras Kumar · 2016-05 · Physics Stack Exchange · on “Variation of Veritasium bullet block experiment”
I'm new here. this is in reference to the video posted by veritasium [this video] on the bullet block experiment. i realise there is already a thread on this [LINK] but i want to ask a variation of the question. so basically we have two identical blocks and we shoot identical bullets at them one at the centre and another off centre. which one will rise higher? now the answer assuming the collision is inelastic is already discussed. but what if the collision were perfectly elastic? i know this is practically impossible but still we have momentum telling us that both blocks must rise to the same height but since no energy is lost as heat, energy tells us that the rotating one must rise to a lower h
Cites rob · 2020-10 · Physics Stack Exchange · on “Impulse given to a rotating rod at the centre VS the end”
If you have an external impulse, you don't have an isolated system, and you shouldn't be chuffed if you discover that energy has been exchanged with the surroundings via the momentum-changing interaction. Your particular example — a rod which receives the same impulse at the middle or at the end — is a famous example of an inelastic-collision experiment which confuses people; see for example this brief Veritasium video [this video] and links therein.