# Homework Help: The relationship between normal force and contact

1. Oct 10, 2011

### siriux

"If there's no normal force, there's no contact."

Is the statement above correct?

What is the relationship between contact and the existence of normal force? Are they necessary and sufficient conditions to each other?

2. Oct 10, 2011

### SammyS

Staff Emeritus
Why can't there be contact without a normal force?

3. Oct 10, 2011

### siriux

I agree with you SammyS but the statement appears in Physics by Randall D. Knight pg225 paragraph 2 which precisely says

Did I understand this quote correctly?

4. Oct 10, 2011

### SammyS

Staff Emeritus
If that's it in its entirety, then you did.

However it is true that: No contact means no normal force.

5. Oct 10, 2011

### siriux

Sorry I missed a full stop.

So according to the textbook, "no contact" is the sufficient condition of "no normal force", which I think is wrong while I agree its conversion ("No contact" means "no normal force".) is right as you've just said.

6. Oct 11, 2011

### Staff: Mentor

Name the force/s that may arise when bodies are in contact.