If someone calls you stupid and this prompts you to go back to college, this comment was an example of the impetus you needed to go back to college.
The outbreak of World War II in 1939 gave a new impetus to receiver development.
Origin of impetus
From American Heritage Dictionary of the English Language, 5th Edition
- From Latin impetus (“a rushing upon, an attack, assault, onset”), from impetere (“to rush upon, attack”), from in (“upon”) + petere (“to seek, fall upon”).