What is the pressure exerted when a force of 20 n is applied to an object over an area of 2 m2 ?

(20 N)/(2 m²) = (20/2) N/m² = 10 Pa

The pascal (Pa) is the derived SI unit of pressure equal to 1 N/m².

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.