Consult your doctor if: 1  Your headache symptoms occur more than 15 days a month or require frequent over-the-counter pain medicine. 2  You have a severe headache, and over-the-counter pain medicine doesn't help. 3  You miss school or work because of frequent headaches or the headaches interfere with your daily life. 4  Definition. Causes.
Newton's law of gravitation. (nt'nz) The principle that expresses the force of gravitational attraction between two bodies as a function of their mass and their distance.
Newtonâs Laws of Motion 1. A body continues at rest in uniform motion in a straight line unless a force is imposed on it. (Inertia) 2. Change of motion is proportional to the force and is made in the same direction. F = ma Force = mass x acceleration acceleration= change in velocity per time