A light passenger vehicle weighing 1470 N collides with a train engine weighing 1.23 x 10^5
N, which was being moved from one rail siding to another. The train engine and the vehicle were entangled after the accident and from your measurements you have been able to determine they skidded 15 m before finally coming to rest at an angle of 68 degress to the crossing. The co-efficient of friction between the vehicle’s tyres and wet road surface
are 0.25. The eyewitness reports highlight the passenger vehicle drove straight through the stop sign and ignored the warning horn blasts of the train and continued onto the railway level crossing without due care. You need to ascertain the vehicle’s actual entrance speed to the crossing and whether the driver has exceeded the speed limit of 60 km/hr?
F = μ * m * g
W = f * d
KE = 1/2mv^2
x component of momentum: (m1 + m2) * Vf * cos θ = m1 * v1i
y component of momentum: (m1 + m2) * Vf * sin θ = m2 * v2i
1470N = 150kg
1.23x10^5 = 12551kg
total mass = 12701kg
The Attempt at a Solution
I made the train (m1) travel in the x direction and the car (m2) is the y direction.
Ff = 0.25 * (12701) * 9.8 = 31117.45 N
W = f*d = 31117.45 * 15 = 466761.75J
KE = 466761.75 = 1/2 mv^2
v = 8.57 m/s
y component (car) = (12701)(8.57)(sin68) = 150 v2
v2 = 672.81 m/s
Now obviously thats alot and i think it has to do with the fact that the car only weights 150kg so I think they made a mistake in the question. If I change the initial mass to 14700N I get a final result of 74.4 m/s (267.84 km/h) which also seems like alot for a car.