This link to a web page in Desktop English contains a very helpful explanation about the various meanings of up in phrasal verbs: http://desktopenglish.net/up-phrasal-verbs-and-preposition/
One meaning of act up is to behave badly, to misbehave, especially in public.
- I made sure my little son had a nap before we went shopping. He acts up when he gets too tired.
Act up can refer to a medical condition that sometimes gets worse.
- He hates rainy weather. That’s when his arthritis acts up.
When a piece of machinery or an instrument like a computer appear to be having a problem, you can say it is acting up.
- I spent a lot of time reloading files today. My computer is really acting up.
- The car did not come to a smooth stop at traffic lights. The brakes act up in hot weather.
One meaning of back up is to drive a vehicle backwards.
- Gary drove into the narrow parking lot. There were no spaces and he could not turn around. He had to back up to the entrance.
You back up a computer file when you make a copy for the sake of safety.
- You don’t want to lose hours of work, do you? Be sure to back up your files regularly.
You back up a person when you provide support to him, especially by saying that he is telling the truth.
- Jim told our manager how the accounting department was to blame for the delay in the project. I backed up my colleague.
- I backed my colleague up.
Traffic backs up when a line of stopped vehicles becomes noticeably long.
- Honey, I’m afraid I’ll be home a little late. There was an accident on the highway. Traffic is backed up for at least three miles.
When a pipe line for water or any other liquid backs up, something is blocking the flow of the liquid.
- What a mess we have in our house. The sewer line has backed up into the basement.
To beat up means to strike or kick repeatedly, causing serious injury.
- Gary shouldn’t have insulted Theresa in public. Her brothers beat up Gary badly.
- Her brothers beat Gary up badly.
The phrasal verb blow up can have many different meanings. One meaning of blow up is to explode or cause to explode.
- The resistance fighters were active all night. They blew up three bridges.
- They blew three bridges up.
- Make sure you don’t overcharge the battery. Otherwise it could blow up.
You can use blow up to describe the change when the weather changes from calm to windy.
- I think maybe you should take a sweater with you. It’s starting to blow up.
Another use of blow up describes when a person suddenly shows extreme anger.
- He didn’t expect any increase in his property tax. When he saw his tax bill he just blew up.
When you inflate a rubber raft or a balloon you are blowing it up.
- First she set up the tent. Then she blew up the air mattress.
- Then she blew the air mattress up.
When you blow up a photograph you are making the image larger.
- He fell in love with one of his photos from his vacation. He blew up the photo to poster size.
- He blew the photo up to poster size.
To bring up a child is to take care of the child from infancy until he is ready to leave home.
- Some people don’t realize the effort it takes to be a good parent. It isn’t easy to bring up children.
- It isn’t easy to bring children up.
Bring up can mean to mention a topic for discussion.
- I know you don’t like talking about your father’s business. I won’t bring up that subject again.
- I won’t bring that up again.
When a person is brought up on charges, he is accused of a crime and has to go to court.
- They found the missing wallet in his overcoat pocket . He was brought up on a charge of robbery.