Key ideas1 of 3
Balanced forces and motion
Newton’s first law: if the resultant force on an object is zero, a stationary object remains stationary, and a moving object continues at constant velocity. Constant velocity means constant speed in the same direction. The stationary car in the example has a 400 N push balanced by 400 N static friction. The moving car has a 400 N driving force balanced by 400 N resistance. Each car has zero resultant force and zero acceleration.
