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.
the tendency of an object to resist a change in motion. Newton's 1st Law of Motion An object at rest tends to stay at rest and an object in motion remains in motion unless acted on by an unbalanced force. Newton's 2nd Law of Motion The acceleration of an object depends on the mass of the object and the force applied. A math equation that represents this law is: force = mass x acceleration (F=m x a)