my car can run across another,why?

carBody=NxScene->createBody(name+";"+filename, new NxOgre::TriangleMeshShape(filename), Vector3(0,0,0),"mass:1");

there is a static plane in the world,and my car can easily run on the plane,collision with plane

then I put several cars on the ground,and drive my car rush towards them,the miracle occured! My car run across them,why??

If i'm not wrong, triangle mesh shape doesn't work with dynamic bodies.

If i'm not wrong, triangle mesh shape doesn't work with dynamic bodies.
If triangle mesh shape doesn't work with dynamic bodies, how can I calculate the boundingbox size of ogre mesh?

Ogre::AxisAlignedBox charAAB = mEntity->getBoundingBox();
Ogre::Vector3 min = charAAB.getMinimum();
Ogre::Vector3 max = charAAB.getMaximum();
Ogre::Vector3 center = charAAB.getCenter();
Ogre::Vector3 size( fabs( max.x - min.x), fabs( max.y - min.y), fabs( max.z - min.z ) );

then just use size.x, size.y and size.z in CubeShape.

I use ConvexShapde(meshname),and the collision happens!

yes convex shape works as well