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Name:  Ki Y.
Status: student
Age: 20s
Location: N/A
Country: N/A
Date: 2000-2001

In the f=ma equation we have taken f~m & f~a .Then we get f=k(ma). How can we take k=1.By practically? or is the definition of the force says it.

Remember, the force f, the mass m, and the acceleration a are all dimensioned quantities, that is they have "units". The mass for example has units of mass e.g. kilograms, pounds. The acceleration has units of meters/(sec^2) , feet/(min^2) etc. and so on. So the numerical value we assign to let's say the force, f, depends upon which units of mass and distance we use to do the measurement or do the computation.

Vince Calder


We set the proportionality constant by defining units to make it so. In metric units, the "Newton" is defined as the force that will give 1 kilogram of mass an acceleration of 1 m/s^2. This sets the constant to 1 if you use m/s^2 for acceleration, kilograms for mass, and Newtons for force. In the British system, a common acceleration is feet/sec^2. The common force is pounds. The mass unit is called a slug. 1 slug is the mass to which 1 pound of force provides an acceleration of 1 ft/s^2. Physicists try to define their units for convenience. F=ma is much more convenient than F=0.278ma.

Dr. Ken Mellendorf
Illinois Central College

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