Question

如下图所示，是一辆汽车通过滑轮组将深井中的物体拉至井口的装置图。已知井深12m，物体重，汽车重G_车=3×10⁴N，汽车匀速拉绳子时的拉力，汽车受到的阻力为车重的0.1倍。求：

（1）将物体从井底拉至井口的过程中，汽车拉绳子的拉力对滑轮组做了多少功？

（2）滑轮组的机械效率为多少？（保留一位小数）

（3）若汽车运动的速度为3m/s，则将物体由井底拉至井口需要多长时间？

（4）汽车牵引力为多少？牵引力的功率为多少？

Answer 1

（1）n=3　　   s=3h=3×12m=36m······································································ (1分)

W=Fs=2.2×10³N×36m=7.92×10⁴J·························································· (1分)

（2）η==······················ (2分)

（3）υ_物=1/3υ=1/3×3m/s=1m/s···································································· (1分)

t_物=h/υ_物=12m/1 m/s=12s································································ (1分)[来源:学*科*网]

　　（4）F_牵=F^′+f=F^′+0.1G_车=2.2×10³N+0.1×3×10⁴N=5.2×10³N·························· (1分)

　　　　 P= F_牵υ_汽=5.2×10³N×3 m/s=1.56×10⁴W (1分)