Why are multiple trials important when carrying out an experiment?

What is the order of the moon, earth, and sun in a lunar eclipse and a solar eclipse?

Aboxcar traveling at 12 m/s approaches a string of 5 identical boxcars sitting stationary on the track. the moving boxcar collides and links with the stationary cars and they all move off together along the track. what is the final speed of the cars immediately after the collision? (you may take the mass of each boxcar to be 18,537 kg.)

Which sound characteristic is not affected by the relative motion of an object