Phrasal verbs formed with down usually show a decrease in the value of something. Note that a phrasal verb can be separable or inseparable. The two parts of an inseparable phrasal verb always stays together.

Bring down (= reduce)

The government has vowed to bring the prices down.

The opposition accused the government of doing nothing to bring down the prices of essential commodities.

Go down = decrease

Prices of digital cameras have gone down dramatically over the last couple of years.

Cut down = reduce the value of

We must cut our spending down.

Knock down = cause to fall from an upright to a lying position

She was knocked down by a bus.

Go down = go to a less important place or position

They have gone down to the country for a holiday.

Put your foot down = insist

Cool down = relax

Cool down. We have got nothing to worry about.

Jane was really upset and angry that it took me a while to cool her down.

Calm down = make less excited

I calmed the children down with a story.

Turn down = reduce volume

You had better turn that music down before Dad gets angry.

Water down = reduce the strength of something

You need to water down your argument.