Can you open the padlock puzzle? #shorts

When you open the door for a person visiting you, this behaviour can be considered as

The chest is locked by a number of padlocks. All padlocks must be unlocked in order to open the chest. 12 Copies of the keys to the padlocks are distributed lie next to it, such that any group of 7 or more keys can open the chest should they choose to do so, but any group of less than 7 cannot. What is the minimal number of padlocks required to achieve this?

3 students {A, B, C} tackle a puzzle together and offers a solution upon which majority of the 3agrees. Probability of A solving the puzzle correctly is p. Probability of B solving the puzzle correctlyis also p. Cisa dumb student who randomly supports the solution of either A or B. There is one morestudent D, whose probability of solving the puzzle correctly is once again, p. Out of the 3 memberteam {A, B, C} and one member team {D}, which one is more likely to solve the puzzle correctly.

If you dip your open palm in a bucket full of water, you feel your hand being pushed up. Why?