中考物理冲刺复习-功和机械能-专题1-功训练VIP专享VIP免费

ideological and theoretical qualities and practical working ability, and strive to build a contingent of league cadres with positive work style and high quality. Hold a regular meting of the party secretary every fortnightly, arrange the work of the regiment, fedback the student information. Focus on training junior high school, junior high school secretary of the regiment branch to enable them to raise A firm political conviction, diligent and diligent learning spirit and practical and innovative work style.功一、功 1. 做功的两个必要因素： A. B. 2.定义： 3.表达式： 4. 单位： 国际单位制（SI）: ，简称： ，符号： 1 J =1 二、功的原理 使用机械时，人们所做的功，都不会少于不用机械时所做的功 ，也就是使用任何机械都 。 设：直接用手所做的功 W1，手使用杠杆所做的功 W2实际机械： W2 W1 理想机械： W2 W1 例 1、如图所示的四种情景中，人对物体做功的是例 2、两辆车，大车的重力是小车的 2 倍，在相同的力作用下沿不同粗糙程度的水平路面通过了相同的 路程，则A.力对大车所做的功比小车多 B.力对小车所 做的功多C.力对两辆车所做的功相同 D.难以推断例 3、如图（甲）所示，小华同学用水平力 F 拉着木箱在水平方向上运动了距离 L，则小华对木箱所做的功为 W1= 。小昕同学沿如图（乙）所示的斜面用同样大小的力 F拉着同一木箱在力的方向上运动了距离 L，小昕对木箱所做的功为 W2。则：W2 W1（填“＞”、Strengthen the team connection, strengthen the knowledge education among the students (especially the first grade students), and promote the formation of good school spirit with the influence of the league members. All League branches should start with recommending outstanding students as the development objects of the League, take amateur league schools as the basis, conscientiously do a good job in the work of pre-league education, league membership education, League members' vanguard exemplary consciousness education, excellent le...