1-Police is treated as a plural noun in English.
A police officer /A policeman /A policewoman = Singular
2-People Always plural but person=singular
3-Staff =In most cases, plural, but depends on meaning.
Can be singular OR plural depending on what you mean.
4-Family
When you think of the family as one unit → singular
- My family is very big.
- His family lives in London.
• When you think of the members inside the family → plural
Her family have different opinions.
My family are all coming tonight.
5-Team
Same as “family”: singular or plural depending on meaning.
• Team as a single group → singular
- The team is winning.
- The team has a new coach.
• Team members → plural
- The team are celebrating.
- The team have arrived.
In British English, plural is more common.
In American English, singular is more common.
people → always plural
staff → usually plural
family → singular or plural (depends on meaning)
team → singular or plural (depends on meaning)