Page:NTSB RAR-77-10.pdf/37

 APPENDIX E — 34 —

By the law of conservation of energy

EIBEO+ED+EC+ES+EF

From the preceding energy evaluations 5&9 V02 = 599.000 + 600,000 + 2.232.000 + 270,000 + 11.088.000 Solving for V0

V0 = 164 in [sec

or

Vo = 2;; mph

Note that the energy requirement for overturning the lead car of the impacting consist is very low (approximately 4 percent) in comparison to the total energy available in the collision. This indicates the likelihood of car overturning in any accident situa— tion where the energy transfer mechanism is such that rollover may Occur. Impact on a curve provides such a mechanism since the lateral component of the contact forces between cars will provide an overturning moment about the wheel rail interface. It should also be noted that the major source of energy loss (approximately 75 percent)was in moving the standing consiSt. Any error in the distance this consist moved or in its braking force would have a major effect an the calculated closing speed.

In this analysis the kinetic energy due to the velocity of the cars after the collision was neglected. The following analy- sis justifies this assumption. The drag force on each impacted

Mcar was computed as , ' rd ~ 6,160 lb The deceleration of each car is given by

a - rd g/W; w (6.160)(396)/(56.000) s 42.5 in./sec2

The velocity of the cars just after impact is

v' - aD : J(2)(42.5)(25-12) - 160 in.lsec