题型:问答题 简答题 — Did Jim ____________ a cake for his friend? — Yes, he ____________. [ ]A. made, made B. make, did C. made, did 查看答案
题型:问答题 简答题 如图所示,质量分别为m和M的两物体P和Q叠放在倾角为θ的固定斜面上,P、Q之间的动摩擦因数为μ1,Q与斜面间的动摩擦因数为μ2。当它们从静止开始沿斜面滑下时,两物体始终保持相对静止,则物体P受到的摩擦力大小为[ ]A.0 B.μ1mgcosθ C.μ2mgcosθ D.(μ1+μ2)mgcosθ 查看答案