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Name: Marksdale High School
Status: educator
Age: 40s
Location: N/A
Country: N/A
Date: Thursday, August 22, 2002
Question:
Mine is simple I am just trying to remember the common formula shared by magnetic force and gravity, I teach an eleventh grade physics class and i would like to prove to them they to have the same formulas but unfortunately I cannot find or remember the formula. I appreciate any time you devote to this if any.

Replies:
Marksdale High School,

The forces do not have the same formula. ELECTRIC force and gravitational force have the same kind of formula. 
         Gravity:  F=G(m1)(m2)/r^2

         Electric:  F=k(q1)(q2)/r^2

Both are proportional to 1/(distance-squared). With gravity, masses produce the force. With electric force, electric charges produce the force. Magnetic force depends on the motion of the charges as well as the amount of charge. If you look at the magnetic force between electric currents, the force is proportional to 1/distance, not 1/(distance-squared).

Dr. Ken Mellendorf
Physics Instructor
Illinois Central College


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