Трамвай движется с ускорением a=49,0 см/с. Найти коэффициент трения k, если известно, что 50 % мощности мотора идет на преодоление силы трения и 50%-на увеличение скорости движения.

I think, that it's true. It's better to have one true friend, that will always help you, than to have a 100 of "true" friends, that always forget everything about you, for example your birthday date and etc. Your true friend will always help you, whatever your problem is.