Ways to write "strength"
We say 电力 electric power instead of 电的力量; 马力， horsepower, instead of 马的力量，魄力，guts instead of 魂魄的力量，etc.

We say 有力的反击，effective strike back, instead of 有力量的反击。大力的支持，fully support, instead of 大力量的支持，etc.

we use 力量 as a separate word, e.g, 我们的力量, our strength, 团结的力量， unity,s strengths , 集体的力量，groups power, we don't say 我们的力 or 团结的力。 

There is an idiom, 群策群力，power of team work. 
There is a phrase, 团队的力量， power of team work. 

From the above, I will say 力 and 力量 mean merely same, the difference is 力 mostly used as part of a phrase while 力量 is used as a separate word.