General noun for speed; often used in technical or formal contexts, but also in everyday language. Slightly more formal than 速さ (はやさ).
この車は速力が足りない。
This car lacks speed.
船は速力を上げて進んだ。
The ship increased speed and moved forward.
The ship increased speed after leaving the harbor.
That car was going at quite a high speed.
The ship is proceeding at a speed of 20 knots.