Answer to Question #82836 in Physics for Sayem

Question

F=Kma or KF=ma
Why we write like that
And why we donot calculate value of K
Also tell
K in SI and CGS unit

Answer 1

Newton’s second law can be written like that: F=Kma, where K – proportionality coefficient. If you measure mass in [kg], and acceleration in [m/s^2], which represents SI units, K=1. It is simple. If you measure mass in [g], and acceleration in [cm/s^2], you use CGS system and here the force must be calculated this way: F=100000·ma.

Usually SI system is preferable because it simplifies calculations. K=1 in SI because of identity between 1 N and 1 kg·m/s^2. However 1 g·cm/s^2 is equal to 1 dyne and therefore is equal to 〖10〗^(-5) N.