Question

on a plane surface N = mg or
N = -mg I am confused please help with detailed reason because on ncert 11th physics page 104 eq. 5.17 it is written N= mg but it must be N= - mg
because they are in opposite directions please help me ​

Answer 1

Answer:

Hey bro when I was in that class I was also in confusion.

Explanation:

often you got in trouble due to Newton Sir ,

here is a way to just solve the question involved Newton Sir

1. Assume Up and Down direction as + ve and - ve axis
2. put all the force values at the moment as F(net) = m.a(net)
3. The above confusion you will also get in Circular Motion
4. You have to always use pseudo force in these conditions

e.g. We think any object will force downward due to Gravity

So the pseudo force will be upward and We will use N as upward force

As I mentioned firstly you must choose axis as + and - .

If you don't get it, re-study your book explanation

I will suggest you to also read FBD deeply to get this Topic more gently