The doppler effect is the change in of a wave due to the motion of the source and/or receiver.

Yes indeed, that is a true statement.  Truer words are seldom written, and I could not agree with you more.

In case you are asking a question, I can kind of see how this might be a question if there is a blank after "... the change in ..." that is to be filled with one or more new words.

If that is the situation, then the blank can be filled with "frequency or wavelength" .

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.

we're given that v₀ = 0 and a = 5.4 m/s². therefore, since v = at + v₀ for constant acceleration the equation for velocity is

after 28s,

m/s

which i would round to 150 m/s as my final answer