Atrain travels 84 kilometers in 1 hours, and then 85 kilometers in 3 hours. what is its average speed?

Why do some scientists and archeologists think that volta was not the first person to build a battery

Uwill get answer it brainliest will be awarded for →calculate the pressure exerted by a body having a mass of 30kg over an area of contact 400cm2.also explain it for every step there should be

The center of a long frictionless rod is pivoted at the origin, and the rod is forced to rotate in a vertical plane with constant angular velocity \omega. write down the lagrangian for a bead of mass m threaded on the rod, using r as your generalized coordinate, where r, \phi are the polar coordinates of the bead. (notice that \phi is not an independent variable since it is fixed by the rotation of the rod tobe \phi = \omega * t) solve lagrange's equation for r(t). what happens if the bead is initially at rest at the origin? if it is released from any point ro > 0, show that r(t) eventually grows exponentially. explain your results in terms of the centrifugal force m* \omega ^2 *r.