M1 v1 = (m1 + m2)v2.
All of the exponents should be lowered to the bottom right of the letters.
These actions are an example of feedback.
Given that the room has reached the desired temperature, there is no more need for it to be heated, at least until the temperature drops a bit. This is why the thermostat sends feedback about this situation to the heater, which immediately switches off until it is needed again.
Use your feet to stop it since it is soccer you can't use your hands!!!! P.S. you can't use gravity.
The equivalent resistance of resistors connected in parallel is

In our problem, we have 5 identical resistor of resistance

, so their equivalent resistance is

The problem also says that the equivalent resistance is

, so we can find the resistance R of each piece of wire:

In the initial wire, it's like the 5 pieces are connected in series, so the equivalent resistance of the wire is just the sum of the resistances of the 5 pieces:
Because after each impact it loses a fraction of its original energy, because it gets transfered to the floor. this is the reason that a perpetual motion machine is impossible. you cannot have infinite energy, because to perform a task, energy must be spent. hope i helped :3