质量为m=1kg的物体在水平面上,物体与水平面之间的动摩擦因数为μ=0.2.现对物体施加一个大小变化、方向
质量为m=1kg的物体在水平面上,物体与水平面之间的动摩擦因数为μ=0.2.现对物体施加一个大小变化、方向不变的水平力F,为使物体在3s时间内发生的位移最大,力F的大小应...
质量为m=1kg的物体在水平面上,物体与水平面之间的动摩擦因数为μ=0.2.现对物体施加一个大小变化、方向不变的水平力F,为使物体在3s时间内发生的位移最大,力F的大小应如下面的哪一幅图所示( ) A. B. C. D.
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曾曾3
2015-01-20
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物体的最大静摩擦力为f=μmg=2N A、在0-1s内,拉力小于最大静摩擦力,物体静止,1-2s内,a= =1m /s 2 ,位移 x 1 = at 2 = ×1×1m=0.5m ,v 1 =at=1m/s; 2-3s内,a= =3m /s 2 ,位移 x 2 =v 1 t+ at 2 =1×1+ ×3×1m =2.5m,所以总位移为0.5+2.5m=3m; B、在0-1s内,a= =1m /s 2 ,位移 x 1 = at 2 = ×1×1m=0.5m ,v 1 =at=1m/s;1-2s内,a= =-1m /s 2 , 位移 x 2 =v 1 t+ at 2 =1×1- ×1×1m =0.5m,v 2 =v 1 +a 1 t=1-1=0;2-3s内,a= =3m /s 2 ,位移 x 3 = at 2 = ×3×1m=1.5m , 总位移为:0.5+0.5+1.5m=2.5m; C、在0-1s内,拉力小于最大静摩擦力,物体静止,1-2s内,a= =3m /s 2 ,位移 x 1 = at 2 = ×3×1m=1.5m ,v 1 =at=3m/s;2-3s内, a= =1m /s 2 ,位移 x 2 =v 1 t+ at 2 =3×1+ ×1×1m =3.5m,总位移为:1.5+3.5m=5m; D、在0-1s内,a= =3m /s 2 ,位移 x 1 = at 2 = ×3×1m=1.5m ,v 1 =at=3m/s;1-2s内, a= =1m /s 2 ,位移 x 2 =v 1 t+ at 2 =3×1+ ×1×1m =3.5m,v 2 =v 1 +at=3+1m/s=4m/s;2-3s内,a= =-1m /s 2 , 位移 x 3 =v 2 t+ at 2 =4×1- ×1×1m =3.5m,总位移为:1.5+3.5+3.5m=8.5m; 所以D发生的位移最大. 故选D |
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