Awooden block is place at rest on a frictionless incline plane. the block is then release from point a which is at 10m height. it continues to move as it passing point b and c. determine the velocities of the wooden block at point b and c

Here since friction is not present in this case so we will use mechanical energy conservation law

As per this mechanical energy conservation law sum of potential energy and kinetic energy will always remains constant

To find the speed at point B we will have

Now similarly for speed at point C

r=rho l/a where a is the area, l is the length and rho is resistivity so the greater the area the lesser the resistance thats why the earth pin is thicker bcos current follow the shortest path, so less resistive .

what experimental evidence led scientists to change from the previous model to this one?

a few of the positive particles aimed at a gold foil seemed to bounce back.

the colors of light emitted from heated atoms had very specific energies.

experiments with water vapor showed that elements combine in specific proportions.

cathode rays were bent in the same way whenever a magnet was brought near them.