A force can be thought of as a push or pull. Force has both magnitude and direction, therefore it is a vector. From physics and Newton's 2nd law, we know that force is equal to a change in an object's momentum (mass x velocity) which describes the quantity of motion. Often, in the discussion of geology and earthquakes we use terms that describe force and the result of force on the Earth. When a force is applied to an object, the object is said to be under stress. Stress is the deforming force per area. Stress producesstrain, the actual deformation. Stress and strain are related, so it is easy to determine one from the other if you know the value of proportionality, a constant value that relates strain to stress, of the substance that is being deformed (different for each individual material.)

Click here to see the types of forces acting on the earth.


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Last modified on 8/13/98 by Maggi Glasscoe (