Question

题目有点长,详细见补充说明注射器的活塞的面积为1.2cm2,注射针头的截面积为1mm2,当注射器水平放置的时候,用4.9

Answer 1

S1=1.2cm2,S2=1mm2,F=4.9牛,L=4cm

F/S1=(1/2)ρV^2 (V为药液射出速度)

V=(2F/(ρS1))^(1/2)

t=S1*L/(S2*V)=(S1*L/S2)(ρS1/(2F))^(1/2)

=0.53 s