单项选择题
物块重G=20N,用P=40N的力按图示方向把物块压在铅直墙上,物块与墙之间的摩擦系数,f=/4,则作用在物块上的摩擦力等于()
A.20N B.15N C.0 D.10N
A.5kN B.10kN C.15kN D.20kN
A.过A点平行力P B.过A点平行BG连线 C.沿AG直线 D.沿AH直线
A. B. C. D.
A.升温和加压 B.降温和降压 C.降温和加压 D.升温和降压
A.8.9×10-5mol/L,0.036% B.8.0×10-9mol/L,3.2×10-6% C.8.0×10-9mol/L,0.036% D.8.9×10-5mol/L,3.2×10-6%
A.1.34×10-3mol/L B.9.46×10-12mol/L C.1.8×10-5mol/L D.5.56×10-10mol/L
A.5 B.10 C.20 D.-10
A.6 B.24 C.120 D.720
A.1 B.0 C.0.5 D.2