Pure maths, physics, logic (braingames.ru): non-trade-related brain games - page 128

 
Contender:
It always seems to be solved by arranging the circles correctly from the start.
Describe the strategy for any arrangement of circles. And, by the way, its description should consider and justify cases where it cannot be locked.
 
Contender:
It seems to always be solvable if the circles are placed correctly from the start.
The solvability depends critically on the initial placement. On an empty field (only a cat) the solution will not be unambiguous.
 
it looks like we will also need an algorithm for selecting the cat itself
 

Just decided (well, I think so), I'll put it out there:

(5) A hockey player hits the puck, after which it moves on the rough ice. It is possible to tuck or not to tuck the puck (progressive velocity in both cases is the same). In which case will the puck travel further? Air resistance is neglected. The ice does not melt.

Comments:

- my solution is two lines.

- If someone thinks that the problem is about a spherical horse, you can easily replace ice by asphalt. Then the ice doesn't need to melt, and the task is quite realistic. And let the hockey player ride on roller skates, if he's here.

 
Mathemat:

(5) A hockey player hits the puck, after which it moves on the rough ice. It is possible to tuck or not to tuck the puck (consider the forward speed the same in both cases). In which case will the puck travel further? Air resistance is neglected. The ice does not melt.

The twisted puck will not move in a straight line. The problem is both incomprehensible and (imho) incorrect.
 
TheXpert:
A twisted puck will not move in a straight line. The problem is both incomprehensible and (imho) incorrect.
it seems that for a sultana of this problem we just take into account that in a straight line
 
TheXpert:
A twisted puck will not move in a straight line. The task is both incomprehensible and (imho) incorrect.

Pucks move in a straight line, this is a moderator's addition.

If, however, it is not in a straight line - then the question of path comparison. It is solved in this case too.

 
Mathemat:
How does the coefficient of friction of the puck material against the ice depend on speed? If it decreases with increasing speed, then the unwound puck will fly further (IMHO).
 
DmitriyN:
How does the coefficient of friction of the puck material against the ice depend on speed? If it decreases with increasing speed, then the unwound puck will fly further (IMHO).
The coefficient of friction is constant and does not depend on speed. Friction depends only on weight and is equal to mu*m*g.
 
Mathemat:
The friction coefficient is constant and doesn't depend on speed. Friction depends only on weight and is equal to mu*m*g.

In this case, I think the distances will be the same, I don't see any good reason for them to be different. The unwound rubber washer has a slightly larger diameter, but I don't think it plays a significant role.

In addition, the washer has a knurled surface around the circumference and is able to cut some roughness of the ice with this "file" surface, which also does not play a special role.