What is the part of the sound wave called where molecules are expanded and are farther apart?

Rarefactions

Explanation:

The sound waves travel in compressions and rarefactions.

As the name suggests compressions are the areas which particles are closer than their usual positioning.

In rarefactions the vibrating particles can be observed further apart than the usual.

what was the acceleration of the 2 kg cart?

⇒ 16.0 cm/s2

what was the acceleration of the 4 kg cart?

⇒ 8.1 cm/s2

what was the acceleration of the 6 kg cart?

⇒ 5.3 cm/s2

the skeletons of most mammals reach a certain size and then stop growing. however, many animals, including some mammals, keep growing throughout their lives. kangaroos, for example, just keep growing and growing until they die. also, the longer an animal lives the greater the chance it might catch some deadly disease.