Why do tracks laid for high-speed trains have larger radii on their bends?

Question

Please be specific and scientific.

Answer 1

Because of the higher lateral (centrifugal) forces the train would derail otherwise

Answer 2

Physics states that an object in motion will remain in motion unless acted upon by an outside force. This correlates to an object in motion in one direction will resist an attempt to change the direction of motion. This is called intertia. The heavier and faster an object is, the larger the force required to change the direction of motion of the object.

When a high-speed train enters a curve, the shape of the rails imposes a force sideways to the train to change the direction of motion. As the curve continues, more force is applied, relative to the original direction of motion. If the force from the rails gets too high, the train's intertia will take over and cause the train to jump the tracks. To prevent this, the curve radius is enlarged so that the direction-changing force never gets high enough for the train to jump out of the rails.

Slower trains can handle more direction change in a short period of time than faster trains can, hence a faster train needs a larger curve than a slower train, given the same mass of train.

Answer 3

read up on 'uniform circular motion'.

suppose the bend that the train travels is part od a large circle. the train is actually accelerating towards the centre of the circle, even though it has a constant speed.

now, acceleration creates a force (newton secong law of motion [force = mass x acceleration]) and in this case, the force going towards the centre of the circle created by the track is called centrepedal force. also (due to Newtons third law of motion [for object A has on object B = force object B has on object A]) force occur in pairs and the force felt by the passengers on the train (and the train inself) is the 'normal force'.

now the equation for the centrepedal force is:-

force = mass x acceleration = (m*v^2)/r

where m = mass, v = velocity and r=radius of the circle.

we can see that the smaller the radius (i.e. the sharper the bend), the higher the force felt by the train. the same effect is felt if the trains velocity is increases.

therefore faster trains compensate for this extra force by creating wider bends (i.e. larger circles).

Answer 4

The faster the speed, greater the centrifugal force opposing
the turn. So, if the radius were not greater, the train would
derail. The other alternatives would be to slant the rails
towards the axis of the turn or to slow down. However the
engineers did a lot of testing and the solution they adopted
is, by far, the best.

Answer 5

The faster you travel on rails the lager radii you need to get round the bends without coming off the rails.

Centrifugal force.

Answer 6

The force required to cause a body to travel in a circle of radius r is:

F=(mv^2)/r

The weight of the train is

F-mg

The total force on the train is the vector sum of these forces,
so,

1) to reduce the amount of "weight" the rails must withstand,
2) passenger comfort--accelerations greater than 2g are distinctly uncomfortable,
3) to reduce the angle of bank required to prevent the train from derailing by rolling.

Answer 7

'coz the momentum and force of the train trying to carry straight on will cause it to de-rail. Trains don't grip the rails, they run on the tracks which hold the lip of they're wheels. If you go too fast the wheel will just rip off the track and wont be able to support the weight/momentum/forces of the train trying to turn it.

Answer 8

k try an experiment.

get in a car and go at 30 mph and try and do a 90 degree turn.

repeat experiment at 70mph and see what happens.

hence the faster the train, the shallower the curve of the rails on a corner.

Answer 9

to allow for the extra bendiness!

Answer 10

I agree w/ crispy bacon.