So as you already know, they may have some technical meanings.
Force is sometimes measure in kg⋅m⋅s−2, or the Newton. One might express this more fundamentally as mass times acceleration. It can have a more mundane meaning in common speach, e.g., "a tour de force", "by force", etc.
"Our forces were strong enough to defeat the Martian army."
Power is a unit of energy transferred per time, e.g., kg⋅m2⋅s−3 or the Watt. It is the amount of work that is performed in a unit of time, and utilities companies provide it. Also, it has a common meaning.
"My power to persuade isn't always effective."
Strength can also have a meaning in material science, measure as toughness (a very involved and complicated topic). Suffice it to say that it also has a common meaning.
"My strengths are in mathematics."