Can someone please explain to me how in lecture 7 he used Newton's second law to justify that

Fs - mg = ma

Question

Can someone please explain to me how in lecture 7 he used Newton's second law to justify  that

Fs - mg = ma

anonymous · Answer

Hi Manny,

thats just the "force acing on a body" found by two different ways
There are two forces acting on the body : gravity (pushing downwards (= -mg)) and the floor (pushing upwards = Fs).
So the total force acting on the body = Fs - mg
Force acting on a body (by definition) = ma
Hence Fs - mg = ma
Hope this helps...

anonymous · Answer

ma=FORCE, Fs=WORK,mg=WEIGHT. therefore, Fs-mg=ma