Aball is kicked from the top of a building with a velocity of 50 m/s and lands 165 m away from the base of the building.
a) how much time does it take for the ball to hit the ground?

3.1 s

Explanation:

we can assume that this motion has a horizontal projectile motion.

projectile motion happens when  an object is subjected to only gravity. Gravity acts to influence the vertical motion of the projectile, it makes a  vertical acceleration.  

The horizontal motion of the projectile is the result of the constant velocity of the object.We assume no acceleration in the horizontal direction.  

applying motion equations

where

s - distance

u - initial velocity

a-acceleration

t - time

s = ut + (1/2)at²

→ 165 = 50t + 0 (as no acceleration is in horizontal direction)

t = 3.1 s

a.   mass number from atomic number

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.