A phrasal verb is actually more than one word, with the verb being accompanied by a modifying adverb or participle. The effect is a change in the verb's meaning, depending on the adverb or preposition and its placement either immediately after the verb or separated by a noun or pronoun. Though some members of this verb family are intransitive, meaning they cannot have a direct object, many others can and do.
The intransitive types of phrasal verbs will not modify a direct object, however, the transitive types often will. It is fine to say, "He warms up his body before every workout." It is wrong, however, to choose an object with other phrasal verbs like "show up" or "run away." An example of an intransitive phrasal verb in action is "The shipping department is finally catching up," instead of "The shipping department is finally catching up the orders." In the latter example, the only way to make this transitive use acceptable is to insert "to" in front of "the orders," making it an indirect, rather than direct, object.
Many phrasal verbs jam the verb together with an adverb or preposition and nothing in between. Doing that could severely alter the meaning. In other cases, however, phrasal verbs can be used either with or without other modifying words in between. An example of an inseparable arrangement is "I hope there's a way to get around this mountain." When separated, this phrasal verb loses all meaning.
Another type of phrasal verb can be easily separated. This often is necessary to change a sentence's structure without altering its information. Examples include, check out, add up, cut down and raise up. These phrasal verbs can take direct or indirect objects, and they can have modifiers inserted or trailing behind. It just depends on the particular writer's style. It is just as grammatically correct to say, "You cut down that tree," as it is to say, "You cut that tree down." Many of these transitive phrasal verbs can take an object before or after the verb appears, but when a pronoun is used as the object, an insertion is often needed to keep the sentence sounding coherent. For instance, "I looked up my old boss on Facebook," will work, but "I looked up him on Facebook" will not.
More than 1,000 phrasal verbs are available for use. The famous Timothy Leary mantra, "Turn on, tune in, drop out," includes three in a row. The English Club Web site maintains a list of more than 1,000 phrasal verbs, with detailed usage information and examples for each.