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Why bridges are not straight but convex?

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When a bridge is built as a straight line.  The force exerted by a vehicle or body on the bridge is equal to the weight ( mg ) of that object.

But

When the bridge is constructed in a convex shape, then the objects (vehicles) moving on the bridge go in a circular path.  Hence, the equation for balancing forces will be:

mg-\frac{mV^2}{r}=N

where

V = velocity of the vehicle.

 r = radius of curvature of the bridge

 N = normal force exerted by a bridge on the vehicle

Hence the force exerted by vehicles (called the load) is less than the weight ( mg ) of that object.

Thus the stress on the bridge reduces.  Hence the stability of the bridge is better.

 

Posted by

avinash.dongre

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