Ok, now that we know it's pressure pushing the hot air up, what happens after that? The balloon starts going up and the place it left is immediately replaced by the ambient air because as the balloon vacates it's place, the only thing that can replace the small volume it left per unit time...
Consider a pool of water. At any depth there is a pressure which depends on the depth. Now consider a flat slab of material or arbitrary density and immerse it to a any depth. Assume it horizontally orientated and calculate the difference in pressure on the top and bottom. Now calculate the...
Another way to look at it. A two dim problem like this has 4 unknowns given the pre-collision velocities and masses. Conservation of energy gives you one equation and conservation of momentum gives you two additional equations. That's 4 unknowns and 3 equations which is not solvable. You...
Let's say the neutron moves in the +y direction before the collision. It is moving at right angles, let's say along the negative x axis, to this afterward, so the deuteron has acquired a momentum equal to this along the positive x axis. since momentum is conserved. For the same reason, the...
The only case I know when one object has no velocity after elastically colliding with another is when both objects have the same mass and they collide head on. In this case, the colliding object stops, the object hit goes off with the speed of the object which just hit it. Obviously momentum...