Friction and motion

1. Dec 5, 2015

MBBphys

1. The problem statement, all variables and given/known data
The question on this paper is as follows: 'Why is it vital that there is a friction force that opposes motion when two surfaces try to slide across one another?'.
My response was: 'If there was no friction, something will keep on going in one direction if no other forces act on it'.
My teacher has marked this as incorrect and has commented: 'Why will an object not move without friction?'.

To me that comment does not make sense; objects would move without friction! So what does she mean? Thank you

2. Relevant equations
N/A

3. The attempt at a solution
N/A

2. Dec 5, 2015

Rumplestiltskin

I remember this question from a GCSE paper. I was marked correct for citing Newton's first law and that the objects would otherwise remain in motion, so I don't think your teacher makes sense either.

3. Dec 5, 2015

Thanks!

4. Dec 5, 2015

CWatters

It's a very poor question in my opinion. Vital to who? To what?

We couldn't walk or pick up food without friction so obviously it's vital to us but could life even exit without friction? Is friction necessary to form stars? Planets? or is gravity sufficient?