题目

如图a所示的开瓶器，在使用时相当于一个_________（填“省力”或“费力”）杠杆,其杠杆简化图如图b所示（不计自重），O为支点。若动力F1和阻力F2都与杠杆垂直，且AO=6cm，BO=1cm，F1=30N，则F2=   N。 答案：省力    180Eric, a middle-aged fashion designer, is very happy because the clothes be designed have never been ________.A．most popularB．the most popularC．less popularD．more popular