impetus

(n. 3.) 1. force with which a moving body tends to maintain its velocity and overcome resistance; as, the impetus of a cannon ball. 2. driving force; incentive. Ambition is an impetus to work for success.

1- (طبيعيات) قُوَّة الإِندفاع - زَخم - كمّيّة التحرُّك 2- دَافِع - حافِز - باعِث