# Questions on work done and Newton's third law

1. Dec 19, 2012

### Misr

Hello

1- work done to push body forward is greater than to pull body backward
what is the explanation for this?can you draw the two FBD in both cases ?

2- why is nail driven in wooden wall but not in the concrete wall ؟ I guess this is somehow related to Newton's third law

Thanks

2. Dec 19, 2012

### Staff: Mentor

This seems like homework, you should provide some reasoning before we can help.

3. Dec 19, 2012

### Misr

No that's not a homework ..I thought of these questions by myself.

the hammer applies a force on the nail by pulling on it
the nail has an equal reaction in the opposite direction
the nail applies force on the wall
the wall has an equal reaction in the opposite direction
the force of the hammer on the nail is greater than the reaction of the wooden wall so the nail is driven in wood but that's not the case in concrete>>
is my explanation true?if so why the reaction of the wall is different in wood and concrete?
I hope it's a good evidence that my questions are not for homework

4. Dec 19, 2012