a*****V
发帖数: 1 | 1 车重 1153 kg, 自行车+人重 110 kg.
下完雨后水泥地面没水干燥,自行车+人的左侧在停车场出口被撞. 自行车+人被推出半
米停下.
问题,车撞击的初始速度是多少? 先谢. | h**********c
发帖数: 4120 | 2 这种问题力学上很复杂，
我觉得电视上detective channel, forensic file;sherrif 或HP 的专业都应该有手册
差表
如果你buget 允许找个侦探问问价。 | f****i
发帖数: 1 | 3 你妈
只要接受过数学专业的系统训练后，脑子确实都坏掉了，思考问题的方式都是很诡异的
这问题，明显取决于地面摩擦力，你不提供，神仙也解决不了。
【在 a*****V 的大作中提到】
: 车重 1153 kg, 自行车+人重 110 kg.
: 下完雨后水泥地面没水干燥,自行车+人的左侧在停车场出口被撞. 自行车+人被推出半
: 米停下.
: 问题,车撞击的初始速度是多少? 先谢.
| h**********c
发帖数: 4120 | 4 这些人业于也都接点私活
【在 h**********c 的大作中提到】
: 这种问题力学上很复杂，
: 我觉得电视上detective channel, forensic file;sherrif 或HP 的专业都应该有手册
: 差表
: 如果你buget 允许找个侦探问问价。
| a*****V
发帖数: 1 | 5 https://x-engineer.org/undergraduate-engineering/physics/solid-mechanics/how
-to-calculate-friction-force/
自行车+人横向被推,按静摩擦算,橡皮对地面静摩擦系数=1,然后0.8. 车轮怎么估计不
清楚. | a*****V
发帖数: 1 | 6 how about this:
car tires on cobbles: friction coefficient = 0.03
https://www.engineeringtoolbox.com/rolling-friction-resistance-d_1303.html
so the friction force on car = 0.03* 1153*9.81 N, on bike 1*110*9.81 N,
total = 1418.428 N, work done = 1418.428*0.5 = 709.214 J, the energy came
from initial hit
1/2*1153*v^2, so v= sqrt(709.214*2/1153) = 1.109147 m/s.
was the estimated speed too low? what else were missing? | a*****V
发帖数: 1 | 7 轮胎的摩擦系数应当高一点,因为出口处有减速的横格子,可以达到0.073
https://en.wikipedia.org/wiki/Rolling_resistance
不踩闸,总摩擦力 = (0.073*1153+1*110)*9.81 =1904.798 N, 做工1904.798 * 0.5 =
952.399J
速度估计sqrt(952.399*2/1153)= 1.285316 m/s.
动量 = 1481.969 kg.m/s. | a*****V
发帖数: 1 | 8 https://trid.trb.org/view/99932
the coefficient of friction on grooved pavement is higher.
coef.f speed m/s
[1,] 0.14 1.519640
[2,] 0.15 1.551582
[3,] 0.16 1.582879
[4,] 0.17 1.613569
[5,] 0.18 1.643687
[6,] 0.19 1.673262
[7,] 0.20 1.702324
[8,] 0.21 1.730898
[9,] 0.22 1.759007
[10,] 0.23 1.786675
[11,] 0.24 1.813920
[12,] 0.25 1.840762
[13,] 0.26 1.867219
[14,] 0.27 1.893306
[15,] 0.28 1.919038
[16,] 0.29 1.944430
[17,] 0.30 1.969494
[18,] 0.31 1.994243
[19,] 0.32 2.018689
[20,] 0.33 2.042843
[21,] 0.34 2.066714
[22,] 0.35 2.090312 | m*****e
发帖数: 1506 | 9 要是撞飞了就得考虑空气摩擦力
【在 f****i 的大作中提到】
: 你妈
: 只要接受过数学专业的系统训练后，脑子确实都坏掉了，思考问题的方式都是很诡异的
: 这问题，明显取决于地面摩擦力，你不提供，神仙也解决不了。
| k**u
发帖数: 10502 | | a*****V
发帖数: 1 | 11 修正一下,
推了不止半米,能到80+cm,另外出口处是一坡度为2.66度的带槽路面,3.02X2米宽,双向
道.
过两天再去测一下,取均值.
coef.f speed m/s
[1,] 0.14 1.700875
[2,] 0.15 1.746358
[3,] 0.16 1.790687
[4,] 0.17 1.833944
[5,] 0.18 1.876204
[6,] 0.19 1.917533
[7,] 0.20 1.957989
[8,] 0.21 1.997627
[9,] 0.22 2.036493
[10,] 0.23 2.074631
[11,] 0.24 2.112081
[12,] 0.25 2.148878
[13,] 0.26 2.185055
[14,] 0.27 2.220644
[15,] 0.28 2.255670
[16,] 0.29 2.290162
[17,] 0.30 2.324141
[18,] 0.31 2.357631
[19,] 0.32 2.390651
[20,] 0.33 2.423222
[21,] 0.34 2.455360
[22,] 0.35 2.487084
[23,] 0.36 2.518407
[24,] 0.37 2.549346
[25,] 0.38 2.579914
[26,] 0.39 2.610124
[27,] 0.40 2.639989
[28,] 0.41 2.669519
[29,] 0.42 2.698726
[30,] 0.43 2.727620
[31,] 0.44 2.756212
[32,] 0.45 2.784510
[33,] 0.46 2.812523
[34,] 0.47 2.840260
[35,] 0.48 2.867728
[36,] 0.49 2.894937
[37,] 0.50 2.921891
[38,] 0.51 2.948600
[39,] 0.52 2.975068
[40,] 0.53 3.001303
[41,] 0.54 3.027311
[42,] 0.55 3.053097
[43,] 0.56 3.078668
[44,] 0.57 3.104027
[45,] 0.58 3.129181
[46,] 0.59 3.154135
[47,] 0.60 3.178892
[48,] 0.61 3.203459
[49,] 0.62 3.227838
[50,] 0.63 3.252035
[51,] 0.64 3.276053
[52,] 0.65 3.299896
[53,] 0.66 3.323568
[54,] 0.67 3.347072
[55,] 0.68 3.370413
[56,] 0.69 3.393593
[57,] 0.70 3.416616
[58,] 0.71 3.439485
[59,] 0.72 3.462203
[60,] 0.73 3.484772
[61,] 0.74 3.507197
[62,] 0.75 3.529479
[63,] 0.76 3.551621
[64,] 0.77 3.573626
[65,] 0.78 3.595496
[66,] 0.79 3.617234
[67,] 0.80 3.638842
[68,] 0.81 3.660323
[69,] 0.82 3.681678
[70,] 0.83 3.702911
[71,] 0.84 3.724022
[72,] 0.85 3.745014
[73,] 0.86 3.765889
[74,] 0.87 3.786649
[75,] 0.88 3.807296
[76,] 0.89 3.827831
[77,] 0.90 3.848257
[78,] 0.91 3.868575
[79,] 0.92 3.888787
[80,] 0.93 3.908894
[81,] 0.94 3.928899
[82,] 0.95 3.948802
[83,] 0.96 3.968605
[84,] 0.97 3.988310
[85,] 0.98 4.007918
[86,] 0.99 4.027431
[87,] 1.00 4.046850 | F********r
发帖数: 878 | 12 Too many possibilities. Did the driver step on the break? how hard? Did
it skid? Was the surface dirty and therefore became muddy with a little
rainfall? | a*****V
发帖数: 1 | 13 hours/cumulative precipitation amount (mm)
0 2.7
1 7.1
2 7.2
3 7.2
4 7.2
The two-way traffic sloped surface was clean and grooved, no rain during the
hours 2-3,3-4,and 4-5. It was highly likely the driver stepped on the
brakes, but in the calculation I assumed not.
【在 F********r 的大作中提到】
: Too many possibilities. Did the driver step on the break? how hard? Did
: it skid? Was the surface dirty and therefore became muddy with a little
: rainfall?
|
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