This sounds like a homework question.
But loosely, understanding psychology will give you an appreciation of each individual's reaction to his or her environment. Social work is usually aimed at people who need it - people who are depressed, impoverished, or in a bad environment. Not all people who are depressed or poor are the same, not all of them have had the same backgrounds, and so not all of them need the same solutions.
Psychology will help a social worker understand what can help each person best.
Systême silurien du centre de la Bohême / par Joachim Barrande
Helping maintain accurate patient records is a critical part of the medical assistant's work.
Major Events in the History of Psychology (5 of 6)
Social class and social status
Where do Psychological Practitioners Work?
A sample of work by a Grade 4 student with a specific learning disorder