2015高考物理一轮复习课时跟踪检测(七)受力分析 共点力的平衡(一)试题及完整解析答案（2015 college entrance examination physics a review class tracking detection (seven) stress analysis of concurrent force balance (a) and a complete analytic answer questi.doc

2015高考物理一轮复习课时跟踪检测(七)受力分析 共点力的平衡(一)试题及完整解析答案（2015 college entrance examination physics a review class tracking detection (seven) stress analysis of concurrent force balance (a) and a complete analytic answer questi Zhang Bei learning plan system, daily share 2, as shown in Figure 2, 100 of the same size and quality are m and smooth ball, still placed in the L shape smooth board. The angle between the slope and the horizontal plane board AB is 30 deg. Second the size of a force balls on the third ball (A.) for B.48mg C.49mg D.98mg Figure 2 answer: select C with third to 100th of the overall 98 balls as the research object, by the action of three forces, namely gravity and inclined plane AB support force and second small balls of third balls in the air force because, in equilibrium, the force along the inclined direction AB should be balanced, so have F23 = 30 ~ 98mgsin = 49mg, so the correct option C. 4, as shown in Figure 4, A, B two still objects on a rough surface, which with a light spring is connected, the length of the spring is greater than the original length. If you use a slow increase from zero level right pull force F object B, until A is mobile, in this process, the change of friction F1 ground on B and on A F2 (A.F1) is the friction decreased after increasing and unchanged unchanged after B.F1 first becomes big and small C.F2 the first larger change after the first D.F2 unchanged unchanged after 4 Clinohedral M 5, placed in the ground level remains at rest tension in the body m along the slope upward, O along the sloping upward from the slant bottom of uniform motion. When the object moves to A, pull F size change, until the object moves to the top of the slope B. Set the objects in the OA section, the friction inclined body on the ground for the Ff1, the ground pressure is FN1; the objects in the AB section, the friction inclined body on the ground for the Ff2, the ground pressure is FN2. The following statement is correct (A.) Ff1Ff2, FN1FN2B. Ff1Ff2,