单选题(5.0分)-|||-3.如图所示,一质量为m的物体静止置于水平桌面-|||-上,假设与桌面的静摩擦和滑动摩擦系数都为μ。-|||-现一水平推力作用在物体上,有 =ct, 其中c是大-|||-于零的常量,t是作用时间,如果作用时间为-|||-=(t)_(2)((t)_(2)gt dfrac (mu mg)(c)) 则此时物体的动量为() ()-|||-F-|||-77177-|||-A dfrac (1)(2)c({t)_(2)}^2-mu mg(t)_(2)+dfrac ({(mu mg))^2}(2c)-|||-B dfrac (1)(2)c({t)_(2)}^2-mu mgt:-|||-C ({t)_(2)}^2-mu mg(t)_(2)-dfrac ({(mu mg))^2}(c)-|||-D ({t)_(2)}^2+mu mgt